Vital nodes identification in complex networks

Real networks exhibit heterogeneous nature with nodes playing far different roles in structure and function. To identify vital nodes is thus very significant, allowing us to control the outbreak of epidemics, to conduct advertisements for e-commercial products, to predict popular scientific publications, and so on. The vital nodes identification attracts increasing attentions from both computer science and physical societies, with algorithms ranging from simply counting the immediate neighbors to complicated machine learning and message passing approaches. In this review, we clarify the concepts and metrics, classify the problems and methods, as well as review the important progresses and describe the state of the art. Furthermore, we provide extensive empirical analyses to compare well-known methods on disparate real networks, and highlight the future directions. In despite of the emphasis on physics-rooted approaches, the unification of the language and comparison with cross-domain methods would trigger interdisciplinary solutions in the near future.

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Solar absorptance of copper–cobalt oxide thin film coatings with nano-size, grain-like morphology: Optimization and synchrotron radiation XPS studies

A Zn/Al layered double hydroxide with molar ratio of 3 was prepared by coprecipitation in alkaline pH and used as a matrix to intercalate the ionic complex diaquadioxalatooxoniobate(V) (DDON), derived from NH4[NbO(C2O4)2(H2O)2]⋅2H2O. In a similar way, the layered zinc hydroxide nitrate, Zn5(OH)8(NO3)2⋅2H2O, was synthesized, preexpanded with azelate ions (−OOC(CH2)7COO−), and then intercalated with the niobium complex. For both layered matrices, the results from X-ray powder diffractometry, Fourier transform infrared spectroscopy, and thermal analysis (TG/s-DTA) indicate the presence of the oxalate ion. In addition, results from X-ray photoelectron and Raman spectroscopy indicate the presence of the niobium center bonded to oxygen atoms. Finally, diffuse reflectance UV–vis spectroscopy suggests that the niobium centers are coordinated to oxalate ions. This is the first report of the intercalation of niobium into a layered matrix.

Intercalation of an oxalatooxoniobate complex into layered double hydroxide and layered zinc hydroxide nitrate.

New cobalt-based metal oxide thin films (MxCoyOz with M = Mn, Cu, Ni) have been deposited on commercial aluminum and glass substrates using sol–gel dip-coating method. The as-deposited films were characterized by a wide range of complementary techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), spectrophotometry and nanoindentation techniques. A light absorption study for coatings on glass substrates within a wavelength range of 300–1100 nm was also conducted. Topographical and morphological investigations showed the presence of nano-sized, grain-like particles in the copper–cobalt oxide coatings, which consequently had the roughest surface among the three coatings. All coatings on glass substrate exhibited higher absorption of ultraviolet (UV) light compared to visible light, while coatings on aluminum substrate generally had low reflectance (< 50%) of UV light, moderate reflectance (< 80%) of visible light and high reflectance (up to 100%) of infrared light. Implications of optical properties as a function of film thickness controlled by dip-heating cycles were discussed. The elastic modulus (E) and hardness (H) of thin film samples compared with stand‐alone commercial aluminum substrate were also measured.

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Optical and mechanical characterization of novel cobalt-based metal oxide thin films synthesized using sol-gel dip-coating method

Copper-cobalt oxide spinels with a common formula Cu x Co3−xO4 (0≤x≤1.0) have been prepared by thermal decomposition at 350° C in air of single-phase mixed basic nitrate precursors (Cu, Co)2(OH)3NO3. The formation of the oxide phase during the thermal treatment has been associated with a diffusionless mode of transformation, established for some hydroxides and hydroxysalts with a layer-type structure.

Preparation of copper-cobalt oxide spinels by thermal decomposition of copper-cobalt basic nitrate mixed crystals

Zinc-cobalt oxide spinels, ZnCo2O4, have been prepared by thermal decomposition of three different precursors: (I) coprecipitated zinc-cobalt hydroxide nitrate; (II) coprecipitated zinc-cobalt hydroxide, and (III) zinc-cobalt hydroxide nitrate prepared by isomorphous replacement of the tetrahedrally coordinated Co2+ ions in the double-layered parent cobalt hydroxide nitrate by Zn2+ ions. It has been shown that the cationic distribution in the oxide product is predetermined by the cationic distribution of the precursor. The coprecipitated precursors (I) and (II) decompose to statistical spinels, whereas precursor (III) decomposes to a normal Zn [Co2]O4 spinet.

K. Petrov

Papers

Preparation of copper-cobalt oxide spinels by thermal decomposition of copper-cobalt basic nitrate mixed crystals

Zinc-cobalt oxide spinels with precursor-controlled degree of inversion

X-ray diffraction measurement of the linear thermal expansion coefficients of WCoB in the range 300 to 973 K