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The composites of porous Co3O4/MWCNTs and porous Co3O4/Co/RGO have been prepared by the wet chemical method and carbonization process. Due to well impedance matching characteristics, dielectric loss properties and highly porous structure Co3O4/Co/RGO composite displays extremely strong electromagnetic wave absorption with a maximum reflection loss of –54.2 dB at 13.14 GHz and the absorption bandwidth with the reflection loss exceeding –10 dB is 5.46 GHz (10.24–15.7 GHz) with the thickness of only 2.0 mm. Furthermore, the addition amount of the composite into paraffin matrix is merely 10 wt %, less than that of most EMW absorber reported previously. Therefore, Co3O4/Co/RGO composite can be used as a promising lightweight EMW absorbing material. [ABSTRACT FROM AUTHOR]

Composites of porous Co0.5Zn0.5 zeolitic imidazolate framework (CZ-ZIF)-derived binary Co/ZnO with reduced graphene oxide (RGO) have been prepared by a wet chemical method and carbonization process. CZ-ZIF-derived Co/ZnO microframes with diameter of about 250 nm were dispersed onto the surface of RGO nanosheets. The impedance matching of the composite could be adjusted by controlling the weight ratio of RGO to Co/ZnO microframes. Due to its porous structure, excellent impedance matching, and dielectric loss characteristics, the Co/ZnO/RGO composite exhibited maximum reflection loss (RL) of − 52.2 dB at 10.96 GHz. Coatings with thickness of 2.0 mm to 4.0 mm showed bandwidth of 5.6 GHz (from 8.72 GHz to 14.32 GHz) for RL of − 10 dB (90% absorption). Additionally, the amount of composite added into paraffin matrix was only 8 wt.%, less than for most electromagnetic (EM) wave absorbers in previous reports. Therefore, such Co/ZnO/RGO composites may be promising candidate EM wave absorbing materials. [ABSTRACT FROM AUTHOR]

The role of the counter electrode (CE) in dye-sensitized solar cell (DSSC) is to collect electrons from the external circuit and reduce I to I in the electrolyte. In this paper, the perovskite-phase LaSrCoO (LSCO) nanoparticles were synthesized through a sol-gel method and used as the CE for DSSC. The cell showed a power conversion efficiency ( PCE) of 3.24 %. To further improve the PCE of CE of the LSCO nanoparticles, the nanocomposites of the LSCO nanoparticles with reduced graphene oxide (LSCO@RGO) have been prepared via a simply physical mixing method and served as the efficient CE for DSSC. The LSCO@RGO nanocomposites exhibit excellent electrocatalytic performance for reduction of triiodide, owing to the positive synergetic effect between LSCO nanoparticles and RGO sheets. As a consequence, the DSSC with the LSCO@RGO nanocomposites CE yielded a PCE of 6.32 %, which is observably higher than that of using pristine LSCO CE (3.24 %) or RGO CE (4.54 %) alone, and up to 88 % of the Pt CE (7.18 %). [ABSTRACT FROM AUTHOR]

It is well-known that hyponormal operators have many interesting properties, for example, if the restriction $$T|_{{\mathcal {M}}}$$ of the hyponormal operator T on its nontrivial closed invariant subspace $${\mathcal {M}}$$ is normal, then $${\mathcal {M}}$$ reduces T. In order to discuss the reducibility of invariant subspaces of an operator, four properties of invariant subspaces ( $$R_{i}, i=1,\ldots ,4$$ ) are introduced. Among others, it is proved that, for a k-quasi- A( n) operator T, if the restriction $$T|_{{\mathcal {M}}}$$ is normal and injective, then $${\mathcal {M}}$$ reduces T, thus the function $$\sigma :T\longmapsto \sigma (T)$$ is continuous on the class of k-quasiclass- A( n) operators. Some examples related to class A( n) and n-paranormal operator are given which imply that the inclusion relations are strict. [ABSTRACT FROM AUTHOR]

Let n be a positive integer, an operator T belongs to class A( n) if $$|T^{1+n}|^{2/(1+n)} \geq |T|^{2}$$ , which is a generalization of class A and a subclass of n-paranormal operators, i.e., $${\parallel}T^{1+n}x{\parallel}^{1/(1+n)} \geq {\parallel}Tx{\parallel}$$ for unit vector x. It is showed that if T is a class A( n) or n-paranormal operator, then the spectral mapping theorem on Weyl spectrum of T holds. If T belongs to class A( n), then the nonzero points of its point spectrum and joint point spectrum are identical, the nonzero points of its approximate point spectrum and joint approximate point spectrum are identical. [ABSTRACT FROM AUTHOR]

Inspired by the problem of powers of hyponormal operators, this paper is to discuss the structure on powers of p-hyponormal and log-hyponormal operators. The structure on powers of operators consists of same-side structure and different-side structure. The same-side structure means relations between $$T^{{*}^{n+m}} T^{n+m}$$ and $$T^{{*}^{n}} T^n ({\rm or} T^nT^{{*}^{n}}\,{\rm and}\,T^{n+m}T^{{*}^{n+m}})$$ , and the different-side structure means relations between $$T^{{*}^{m}} T^{m}\,{\rm and}\,T^{n}T^{{*}^{n}}$$ where m, n are positive integers and T is a bounded linear operator on a Hilbert space. Thus, the original problem of powers of hyponormal operators belongs to different-side structure on powers of hyponormal operators. The structure on powers of p-hyponormal operators for p > 0 is emphasized. Also, some applications are obtained. [ABSTRACT FROM AUTHOR]