Time filter

Source Type

Zhan N.,Xinyang Vocational and Technical College | Wu L.,China Jiliang University
Procedia Engineering | Year: 2012

The minimum spanning tree problem is a classical and well-known combinatorial optimization problem. There exist many efficient algorithms such as the Kruskal algorithm and Prim algorithm to solve it. But in a real network, the vertices as well as the edges may have weights, and there are many cases of the vertex weights according to the degrees of the vertices. In this paper, we consider the computational complexity of the minimum expense spanning tree problem, which is to find a spanning tree in a network with minimum total expenses. We show that this problem is NP-hard in some general situations. And we propose a polynomial time algorithm when computing all the weights of the vertices in a spanning tree. © 2012 Published by Elsevier Ltd.

Yang P.,Harbin Institute of Technology | Zhao Y.,Harbin Institute of Technology | Su C.,Xinyang Vocational and Technical College | Yang K.,Harbin Institute of Technology | And 2 more authors.
Electrochimica Acta | Year: 2013

Electrodeposition of Cu-Li alloy from 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) ionic liquid was investigated. The cyclic voltammetry behaviors of [BMIm][BF4] containing Cu(II), Li(I), and mixtures of Cu(II) and Li(I) were studied at a copper working electrode, separately. The Cu-Li alloy produced by direct current electrodeposition was characterized by inductively coupled plasma atomic emission spectrometry (ICP), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The function of 2-butyne-1,4-diol was studied by linear sweep voltammetry. The result shows that the 2-butyne-1,4-diol could improve Li content in deposit, and make the Cu-Li alloy deposits denser and finer. © 2012 Elsevier Ltd. All rights reserved.

Zhang Q.,Lanzhou University of Technology | Mei J.,Lanzhou University of Technology | Wang X.,Lanzhou University of Technology | Fan W.,CAS Chengdu Institute of Organic Chemistry | And 3 more authors.
Journal of Alloys and Compounds | Year: 2014

Ultrathin LiMn2O4 was successfully prepared by calcinating at 700 °C following solution combustion synthesis. The effects of NO3 -/CH3COO- ratio of starting materials on the structure and electrochemical performance are investigated. XRD results indicate that LiMn2O4 samples prepared with a NO3 -/CH3COO- ratio of 3:2 (LMO3) has the smallest nanocrystallite of 36.1 nm. SEM results reflect that LMO3 has the smallest average primary particles of 210 nm. These features ensure LMO3 have the excellent electrochemical performance. It even can deliver a capacity of 95.5 mA h g-1 at charge-discharge rate of 10 C. The charge-discharge voltage profiles, dQ/dV versus voltage curves and EIS test all indicate LMO3 has the best electrochemical performance. © 2014 Elsevier B.V. All rights reserved.

Liu L.-L.,Heilongjiang Institute of Science and Technology | Liu L.-L.,Harbin Institute of Technology | Yang P.-X.,Harbin Institute of Technology | Su C.-N.,Xinyang Vocational and Technical College | And 2 more authors.
International Journal of Electrochemical Science | Year: 2013

The microstructure, composition and elemental depth profile of micro-arc oxidation film was analyzed by means of Scanning Electron Microscope (SEM), X-ray diffraction (XRD) and Energy Disperse Spectroscopy (EDS). The film is composed of an outer loose layer and an inner dense layer, a few circular pores present on the film surface, but merely in the outer loose layer, do not traverse through the inner dense layer to the metal substrate. The film is composed of forsterite phase Mg2SiO4 and magnesia MgO. The elemental depth profile shows that Mg, Si and O have a gradient distribution within the film. The gradient distribution of Mg, Si, O also indicated that the relative content of Mg2SiO4 decreased, while MgO increases in the depth direction to the alloy substrate. Combined with the impedance spectra collected after different exposure time to 3.5 % NaCl solution, a four-stage corrosion process was proposed to describe the corrosion behavior of micro-arc oxidation film on magnesium alloy. © 2013 by ESG.

Luo J.H.,Chengdu University of Technology | Luo J.H.,Xinyang Vocational and Technical College
Applied Mechanics and Materials | Year: 2014

The removal of persistent organic pollutants (POPs) in soils at initial concentrations ranging from 20.00 to 321.05 mg·kg-1 was investigated under different planting patterns, and enhancement mechanisms were analyzed. Results showed that the dissipation of POPs in soils growing Brassica campestris and Medicago sativa significantly exceeded those vegetating single species. During 70-day experiment, about 75.06% of Pyr and 68.22% of BaP was removed from the soils under mixed cropping; while only 31.8% and 64.03% of Pyr and 27.84% and 51.93 of BaP were removed under single rape and alfalfa cropping, respectively. Of all pathways enforcing POPs removal, plant-microbial interactions is the most predominant. These results suggested a feasibility of the establishment of multi-species phytoremediation for improvement of the remediation efficiencies of POPs, which may decrease accumulations of POPs in crops and thus reduce their risks. © (2014) Trans Tech Publications, Switzerland. All Rights Reserved.

Discover hidden collaborations