280 research outputs found
The signless Laplacian spectral radii of modified graphs
In this paper, various modications of a connected graph G are regarded as perturbations of its signless Laplacian matrix. Several results concerning the resulting changes to the signless Laplacian spectral radius of G are obtained by solving intermediate
eigenvalue problems of the second type
Solar Panels Based on a Flexible Material the Quad-Rotor UAV System
In view of the current practical application of solar UAV, insufficient endurance, poor stability, poor practicality and low solar energy utilization. We have designed a new four-rotor drone aircraft with solar energy and flexible materials (such as perovskite) as solar panels
Embedding Knowledge Graph of Patent Metadata to Measure Knowledge Proximity
Knowledge proximity refers to the strength of association between any two
entities in a structural form that embodies certain aspects of a knowledge
base. In this work, we operationalize knowledge proximity within the context of
the US Patent Database (knowledge base) using a knowledge graph (structural
form) named PatNet built using patent metadata, including citations, inventors,
assignees, and domain classifications. We train various graph embedding models
using PatNet to obtain the embeddings of entities and relations. The cosine
similarity between the corresponding (or transformed) embeddings of entities
denotes the knowledge proximity between these. We compare the embedding models
in terms of their performances in predicting target entities and explaining
domain expansion profiles of inventors and assignees. We then apply the
embeddings of the best-preferred model to associate homogeneous (e.g.,
patent-patent) and heterogeneous (e.g., inventor-assignee) pairs of entities
The algebraic connectivity of lollipop graphs
AbstractLet Cn,g be the lollipop graph obtained by appending a g-cycle Cg to a pendant vertex of a path on n-g vertices. In 2002, Fallat, Kirkland and Pati proved that for n⩾3g-12 and g⩾4, α(Cn,g)>α(Cn,g-1). In this paper, we prove that for g⩾4, α(Cn,g)>α(Cn,g-1) for all n, where α(Cn,g) is the algebraic connectivity of Cn,g
On the kth Laplacian eigenvalues of trees with perfect matchings
AbstractLet Tn+ be the set of all trees of order n with perfect matchings. In this paper, we prove that for any tree T∈Tn+, its kth largest Laplacian eigenvalue μk(T) satisfies μk(T)=2 when n=2k, and μk(T)⩽⌈n2k⌉+2+(⌈n2k⌉)2+42 when n≠2k. Moreover, this upper bound is sharp when n=0(mod2k)
Role of the porous structure of the bioceramic scaffolds in bone tissue engineering
The porous structure of biomaterials plays a critical role in improving the efficiency of biomaterials in tissue engineering. Here we fabricate successfully porous bioceramics with accurately controlled pore parameters, and investigate the effect of pore parameters on the mechanical property, the cell seeding proliferation and the vascularization of the scaffolds. This study shows that the porosity play an important role on the mechanical property of the scaffolds, which is affected not only by the macropores size, but also by the interconnections of the scaffolds. Larger pores are beneficial for cell growth in scaffolds. In contrast, the interconnections do not affect cell growth much. The interconnections appear to limit the number of blood vessels penatrating through adjacent pores, and both the pores size and interconnections can determine the size of blood vessels. The results may be referenced on the selective design of porous structure of biomaterials to meet the specificity of biological application
Simulation and Test of Lateral Ballast Resistance to 1435 mm/1000 mm Dual-Gauge Sleepers
The stability of a 1000 mm/1435 mm dual-gauge track is lower than that of a single-gauge track. One of the important factors that affects the stability of the track is the lateral resistance of the track bed. We have established a discrete element simulation model of the dual-gauge sleeper-track bed in PFC to analyse the characteristics of the lateral resistance of the 1000 mm/1435 mm dual-gauge sleeper. With China Type IIIc sleepers as the control group, we carried out the lateral resistance test for the full-scale sleeper model under the same conditions. The research results indicate that the most effective way to increase the lateral resistance of the dual-gauge track bed is to increase the end surface area and bottom area of the sleeper. The application of adjacent sleepers is an effective way to increase the lateral resistance of the track bed further. The research results gained from this study can be used to guide the design of dual-gauge sleepers
Study on Temperature Force Control Mechanism of CRTSⅡ Slab Track: Control Conditions of Temperature Cracking
Diseases such as track slab arching and joint concrete crushing of China Railway Track System (CRTS)II slab track were caused by huge temperature force, which seriously threatens driving safety of trains. In this study, a longitudinal weak connection scheme of CRTSII slab track was proposed to adjust the temperature force in track slab and reduce diseases of longitudinal continuous track slab. This paper focuses on the cracking characteristics of the longitudinal heterogeneous concrete composite structure. The equation which was originally developed to calculate crack width and structure stress under temperature loads, was put forward to consider deformation difference of different elastic modulus. The influence law of various parameters was analyzed. The reinforcement stress and crack width of CRTSII slab track after longitudinal connection weakening were calculated, and the reasonable limit value of tensile force of connection reinforcement and the minimum value of bond resistance of reinforcement in joint position were obtained. The result shows that, in order to reduce the bond resistance between the joint material and the reinforcement, the elastic modulus of the elastic material should be less than 5000 MPa; in order to ensure that the reinforcement does not produce large stress, the elastic modulus of the joint should be greater than 1000 MPa
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