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In this article, a frequency-domain modal parameter estimation method is proposed. The algorithm automatically separates physical poles from mathematical ones. An important issue in the automatization of the algorithm is the inclusion of noise information to estimate the standard deviations of the poles. These standard deviations are used (together with other features) as the inputs of a fuzzy clustering algorithm. The clustering algorithm then classifies the poles into the mathematical and physical ones. The method requires no user interaction, and a parameter is available quantifying the success of the classification. 相似文献
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Hao Wei Dr. Zhi‐Yi Hu Yu‐Xuan Xiao Dr. Ge Tian Dr. Jie Ying Prof. Gustaaf Van Tendeloo Prof. Christoph Janiak Prof. Xiao‐Yu Yang Prof. Bao‐Lian Su 《化学:亚洲杂志》2018,13(9):1119-1123
Highly dispersed PtPd bimetallic nanocrystals with enhanced catalytic activity and stability were prepared by adjusting the interfacial wettability of the reaction solution on a commercial carbon support. This approach holds great promise for the development of high‐performance and low‐cost catalysts for practical applications. 相似文献
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DO Charkin AV Urmanov SM Kazakov D Batuk AM Abakumov S Knöner E Gati B Wolf M Lang AV Shevelkov GV Tendeloo EV Antipov 《Inorganic chemistry》2012,51(16):8948-8955
Three new ternary copper phosphides, Sr(2)Cu(6)P(5), Eu(2)Cu(6)P(5), and EuCu(4)P(3), have been synthesized from the elements in evacuated silica capsules. Eu(2)Cu(6)P(5) and Sr(2)Cu(6)P(5) adopt the Ca(2)Cu(6)P(5)-type structure, while EuCu(4)P(3) is isostructural to BaMg(4)Si(3) and still remains the only representative of this structure type among the ternary Cu pnictides. All three materials show metallic conductivity in the temperature range 2 K ≤ T ≤ 290 K, with no indication for superconductivity. For Eu(2)Cu(6)P(5) and EuCu(4)P(3), long-range magnetic order was observed, governed by 4f local moments on the Eu atoms with predominant ferromagnetic interactions. While Eu(2)Cu(6)P(5) shows a single ferromagnetic transition at T(C) = 34 K, the magnetic behavior of EuCu(4)P(3) is more complex, giving rise to three consecutive magnetic phase transitions at 70, 43, and 18 K. 相似文献
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Tobías G Beltrán-Porter D Lebedev OI Van Tendeloo G Rodríguez-Carvajal J Fuertes A 《Inorganic chemistry》2004,43(25):8010-8017
The crystal structure of the n = 1 member of the Ruddlesden-Popper family (SrO)(SrNbO(2)N)(n) was refined by the Rietveld method using neutron powder diffraction data. This complex crystallizes in the I4/mmm space group with cell parameters a = 4.0506(2) and c = 12.5936(9) angstroms. The refined composition was Sr(2)NbO(3.28)N(0.72), which corresponds to a formal oxidation state for Nb of +4.72, meaning 72% Nb(V) and 28% Nb(IV). The nitrogen atoms order in the equatorial sites of the niobium octahedra according to Pauling's second crystal rule as the more charged anion occupies the site showing the larger bond strength sums. Pauling's second crystal rule is shown to be able to predict the distribution of anions in the available crystallographic sites in other mixed anion systems such as oxyhalides with K(2)NiF(4) structures and other oxynitrides. The defect structure of the n = 1 and n = 2 members of the same family was investigated by high-resolution electron microscopy. Recurrent intergrowth along the c axis with other Ruddlesden-Popper members (n = 3, 4, and perovskite) is observed, resulting in streaking along this direction in the corresponding electron diffraction patterns. 相似文献
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Engineering morphology and size of CeO2‐based nanostructures on a (sub)nanometer scale will greatly influence their performance; this is because of their high oxygen storage capacity and unique redox properties, which allow faster switching of the oxidation state between Ce4+ and Ce3+. Although tremendous research has been carried out on the shape‐controlled synthesis of CeO2, the characterization of these nanostructures at the atomic scale remains a major challenge and the origin of debate. The rapid developments of aberration‐corrected transmission electron microscopy (AC‐TEM) have pushed the resolution below 1 Å, both in TEM and in scanning transmission electron microscopy (STEM) mode. At present, not only morphology and structure, but also composition and electronic structure can be analyzed at an atomic scale, even in 3D. This review summarizes recent significant achievements using TEM/STEM and associated spectroscopic techniques to study CeO2‐based nanostructures and related catalytic phenomena. Recent results have shed light on the understanding of the different mechanisms. The potential and limitations, including future needs of various techniques, are discussed with recommendations to facilitate further developments of new and highly efficient CeO2‐based nanostructures. 相似文献
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Zaikina JV Kovnir KA Sobolev AV Presniakov IA Prots Y Baitinger M Schnelle W Olenev AV Lebedev OI Van Tendeloo G Grin Y Shevelkov AV 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(18):5090-5099
Sn(20.5)As(22)I(8), a new cationic clathrate, has been prepared by using an ampoule technique. According to the X-ray powder diffraction data, it crystallizes in the face-centered cubic space group F23 or Fm(-)3 with a unit-cell parameter of a=22.1837(4) A. Single-crystal X-ray data allowed solution of the crystal structure in the subcell with a unit-cell parameter of a(0)=11.092(1) A and the space group Pm(-)3n (R=5.7 %). Sn(20.5)As(22)I(8) (or Sn(20.5) square(3.5)As(22)I(8), accounting for the vacancies in the framework) possesses the clathrate-I type crystal structure, with iodine atoms occupying the cages of the cationic framework composed of tin and arsenic atoms. The crystal structure is strongly disordered. The main features are a random distribution of vacancies, and shifts of the tin and arsenic atoms away from their ideal positions. The coordination of the tin atoms has been confirmed by using (119)Sn M?ssbauer spectroscopy. Electron diffraction and high-resolution electron microscopy (HREM) analyses have confirmed the presence of the superstructure ordering, which results in a doubling of the unit-cell parameter and a change of the space group from Pm(-)3n to either F23 or Fm(-)3. Analysis of the crystal structure has led to the construction of four ordering models for the superstructure, which have been corroborated by HREM, and has also led to the identification of disordered regions originating from overlap of the different types of ordered domains. Sn(20.5)As(22)I(8) is a diamagnetic semiconductor with an estimated band gap of 0.45 eV; it displays abnormally low thermal conductivity, with the room temperature value being just 0.5 W m(-1) K(-1). 相似文献
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Dr. Laura Cabana Dr. Arántzazu González‐Campo Dr. Xiaoxing Ke Prof. Gustaaf Van Tendeloo Dr. Rosario Núñez Dr. Gerard Tobias 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):16792-16795
As‐produced single‐walled carbon nanotubes (SWCNTs) tend to aggregate in bundles due to π–π interactions. Several approaches are nowadays available to debundle, at least partially, the nanotubes through surface modification by both covalent and noncovalent approaches. Herein, we explore different strategies to afford an efficient covalent functionalization of SWCNTs with cobaltabisdicarbollide anions. Aberration‐corrected HRTEM analysis reveals the presence of metallacarboranes along the walls of the SWCNTs. This new family of materials presents an outstanding water dispersibility that facilitates its processability for potential applications. 相似文献
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Warunee Lueangchaichaweng Neil R. Brooks Sonia Fiorilli Elena Gobechiya Kaifeng Lin Li Li Sonia Parres‐Esclapez Elsa Javon Sara Bals Gustaaf VanTendeloo Johan A. Martens Christine E. A. Kirschhock Pierre A. Jacobs Paolo P. Pescarmona 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(6):1611-1615
Gallium oxide nanorods with unprecedented small dimensions (20–80 nm length and 3–5 nm width) were prepared using a novel, template‐free synthesis method. This nanomaterial is an excellent heterogeneous catalyst for the sustainable epoxidation of alkenes with H2O2, rivaling the industrial benchmark microporous titanosilicate TS‐1 with linear alkenes and being much superior with bulkier substrates. A thorough characterization study elucidated the correlation between the physicochemical properties of the gallium oxide nanorods and their catalytic performance, and underlined the importance of the nanorod morphology for generating a material with high specific surface area and a high number of accessible acid sites. 相似文献