241 research outputs found
Adsorption of molecular oxygen on doped graphene: atomic, electronic and magnetic properties
Adsorption of molecular oxygen on B-, N-, Al-, Si-, P-, Cr- and Mn-doped
graphene is theoretically studied using density functional theory in order to
clarify if O2 can change the possibility of using doped graphene for gas
sensors, electronic and spintronic devices. O2 is physisorbed on B-, and Ndoped
graphene with small adsorption energy and long distance from the graphene
plane, indicating the oxidation will not happen; chemisorption is observed on
Al-, Si-, P-, Cr- and Mn-doped graphene. The local curvature caused by the
large bond length of X-C (X represents the dopants) relative to CC bond plays a
very important role in this chemisorption. The chemisorption of O2 induces
dramatic changes of electronic structures and localized spin polarization of
doped graphene, and in particular, chemisorption of O2 on Cr-doped graphene is
antiferromagnetic. The analysis of electronic density of states shows the
contribution of the hybridization between O and dopants is mainly from the p or
d orbitals. Furthermore, spin density shows that the magnetization locates
mainly around the doped atoms, which may be responsible for the Kondo effect.
These special properties supply a good choice to control the electronic
properties and spin polarization in the field of graphene engineering.Comment: 7 pages, 10 figure
The proof of a conjecture on largest Laplacian and signless Laplacian H-eigenvalues of uniform hypergraphs
Let and be the adjacency tensor, Laplacian tensor and signless Laplacian
tensor of uniform hypergraph , respectively. Denote by the largest H-eigenvalue of tensor . Let be a
uniform hypergraph, and be obtained from by inserting a new
vertex with degree one in each edge. We prove that Denote by
the th power hypergraph of an ordinary graph with maximum degree
. We will prove that
is a strictly decreasing sequence, which imply Conjectrue 4.1 of Hu, Qi and
Shao in \cite{HuQiShao2013}. We also prove that
converges to when goes to
infinity. The definiton of th power hypergraph has been generalized
as We also prove some eigenvalues properties about which generalize some known results. Some related results
about are also mentioned
On the -index of minimally -(edge-)connected graphs for small
Let be a graph with adjacency matrix and let be the
diagonal matrix of vertex degrees of . For any real ,
Nikiforov defined the -matrix of a graph as . The largest eigenvalue of is called the
-index or the -spectral radius of . A graph is minimally
-(edge)-connected if it is -(edge)-connected and deleting any arbitrary
chosen edge always leaves a graph which is not -(edge)-connected. In this
paper, we characterize the minimally 2-edge-connected graphs and minimally
3-connected graph with given order having the maximum -index for
, respectively.Comment: arXiv admin note: text overlap with arXiv:2301.0338
Bearing fault diagnosis based on active learning and random forest
Bearing plays an important role in rotating machineries and has received increasing attention in diagnosis of its faults accurately. This paper proposes a fault diagnosis approach exploiting active learning (AL) based on random forest (RF), which can perform accurate bearing fault diagnosis with most valuable samples. First, feature vectors are obtained by empirical mode decomposition (EMD) process for original vibration signals and selected as input of the system. Second, samples with highest uncertainty are selected through AL and added to the training set to train RF classifier. Finally, trained RF is employed to perform classification for bearing faults with testing set. Experimental results demonstrate that the proposed approach can effectively and accurately identify typical bearing faults
The post-Paris approach to mitigating Arctic warming—perspectives from shipping emissions reduction
The availability of increased Arctic shipping as a consequence of sea ice decline is a regional issue that is closely linked with international climate governance and global governance of the maritime industry. Sea ice decline creates favorable circumstances for the development of merchant shipping, but is accompanied by increases in greenhouse gas emissions. Reduction of greenhouse gas emissions from the shipping industry is of utmost importance to prevent the destruction of the fragile Arctic ecosystem. This paper focuses on the core content of the Paris Agreement and suggests that the International Maritime Organization could guide the shipping industry to reach a fair agreement with states that includes market-based measures, capacity building, and voluntary actions of shipping companies as non-state actors
- …