Showing papers by "University of Science and Technology Beijing published in 2008"
TL;DR: In this article, the factors of the atomic size difference Delta and the enthalpy of mixing ΔH mιx of the multi-component alloys were summarized from the literatures.
Abstract: The factors of the atomic size difference Delta and the enthalpy of mixing ΔH mιx of the multi-component alloys were summarized from the literatures. The formation zones of solid-solution phases, intermediate phases, and bulk metallic glasses were determined and the validity was verified by experimental results. For forming the solid solution, the alloys should have high entropy of mixing, lower Delta, and not too negative and positive enthalpy of mixing.
1,936 citations
TL;DR: The daily intake of Hg and As through rice was much lower than the tolerable daily intakes, but bioaccumulation of HG through the food chain and intake of As from other food stuff should also be of concern.
517 citations
TL;DR: In this article, the effects of nano-SiC addition on the thermoelectric and mechanical properties of high-density n-type Bi 2 Te 3 materials were studied.
356 citations
TL;DR: Results obtained indicated that this system could be tuned to a great extent because ionic liquids can be designable and the method does not suffer from the limitations of that in conventional solvent micro-extraction.
297 citations
TL;DR: Uniform single-crystalline CeO2 nano-octahedrons and nanorods were synthesized by a facile hydrothermal synthesis process only using Ce(NO3)3·6H2O as cerium resource and Na3PO4·6HO as mineralizer.
Abstract: Uniform single-crystalline CeO2 nano-octahedrons and nanorods were synthesized by a facile hydrothermal synthesis process only using Ce(NO3)3·6H2O as cerium resource and Na3PO4·6H2O as mineralizer,...
295 citations
Journal Article•
TL;DR: Cooperative spectrum sensing in cognitive radio(CR) networks is analyzed and detection probability to primary users can be improved by multi-cooperative users in multi-user networks.
Abstract: Cognitive users need to detect primary users continuously and rapidly.Cooperative spectrum sensing in cognitive radio(CR) networks is analyzed.Cooperative spectrum sensing in the ideal network with two cognitive users can reduce the mean detection time.Detection probability to primary users can be improved by multi-cooperative users in multi-user networks.Finally,the realization of multi-user networks is considered.
267 citations
TL;DR: This proposed method was successfully applied in the analysis of four real environmental water samples and good spiked recoveries were obtained, indicating that temperature-controlled ionic liquid dispersive liquid-phase microextraction had excellent application prospect in environmental field.
237 citations
TL;DR: In this paper, single-crystal tetragonal α-MnO2 nanotubes have been successfully synthesized by a facile hydrothermal treatment of KMnO4 in the hydrochloric acid solution.
Abstract: Single-crystal tetragonal α-MnO2 nanotubes have been successfully synthesized by a facile hydrothermal treatment of KMnO4 in the hydrochloric acid solution. The sample has been characterized by X-ray powder diffraction, field emission scanning electron microscopy, transmission electron microscopy, and orientation dependent Raman spectroscopy, which indicates the nanotubes have high-quality crystalline and shape-dependent optical properties. The morphology evolution of the sample reveals that the nanotubes are formed via the solid nanorod by a chemical etching process.
232 citations
TL;DR: Two fuzzy mean-semivariance models are proposed based on the concept of semivariance of fuzzy variable, and a fuzzy simulation based genetic algorithm is presented to solve portfolio selection problem in fuzzy environment.
229 citations
TL;DR: In this article, the effects of orientation degree and hot-forging temperature on thermoelectric properties were investigated, and the results showed that the electrical resistivity was reduced by increasing orientation degree, the Seebeck coefficient was increased by raising hot forging temperature, and consequently the power factor was significantly increased.
227 citations
TL;DR: The results show that addition of glucose was found favorable not only for cell growth but also for lipid synthesis, and of the three adding methods glucose feedback addition was the most effective one.
TL;DR: Li4−xAlxTi5O12 was synthesized via solid state reaction in an Ar-flowing atmosphere as discussed by the authors, where the substitution of Al for Li site can enhance the electronic conductivity and impede the Li-ion diffusion in the lattice.
TL;DR: In this article, a polymer electrolyte membrane based on poly(vinylidenefluoride-hexafluoropropylene) (PVDF-HFP) was prepared by a phase inversion method.
TL;DR: Direct experimental evidence is given for the fact that thenegative thermal expansion of PbTiO3-based solid solutions is strongly correlated with the temperature dependence of the ferroelectricity, which is a new negative thermal expansion mechanism.
Abstract: PbTiO3−Bi(Zn1/2Ti1/2)O3 and related solid solutions exhibit an unusually negative thermal expansion with considerably enhanced tetragonality and Curie temperature. A zero thermal expansion is found over a wide temperature range of room temperature to 500 °C. Direct experimental evidence is given for the fact that the negative thermal expansion of PbTiO3-based solid solutions is strongly correlated with the temperature dependence of the ferroelectricity, which is a new negative thermal expansion mechanism.
TL;DR: In this article, a multiscale morphology analysis is applied to one-dimensional signal by defining both the length and height scales of structuring elements (SEs) and a local-peak value based adaptive algorithm is also introduced.
TL;DR: In this paper, the authors investigated the SCC behavior of X70 pipe steel in an extracted acidic soil solution by slow strain rate test (SSRT), potentiodynamic polarization curve measurements and surface analysis technique.
TL;DR: In this paper, a three-dimensional ventilated room is simulated by a Lagrangian discrete random walk (DRW) model and two Eulerian models: drift flux model and mixture model.
TL;DR: In this paper, Birnessite-type MnO2 nanowalls have been fabricated on Si(111) substrate by a facile solution method and a magnetic transition temperature of 9.2 K was determined.
Abstract: Birnessite-type MnO2 nanowalls have been fabricated on Si(111) substrate by a facile solution method. The XRD pattern indicates that the sample has the typical feature of turbostratic disorder and prefers to grow in the ab plane. The nanowalls are composed of thin flakes distributing uniformly over the surface of the Si(111) substrate. A magnetic transition temperature of 9.2 K is determined. Prominent magnetic anisotropy with the easy magnetization direction in the ab plane is observed at 5 K.
TL;DR: In this article, a steel matrix composite reinforced with TiB2 and TiC reinforcements (30 to 70wt) has been produced through the synthesis reaction from Ti, C and FeB.
TL;DR: In this paper, a 3D numerical model was developed to explore the effects of the cathode flow channel configuration on the local transport phenomena and cell performance for parallel and interdigitated flow fields in proton exchange membrane (PEM) fuel cells.
TL;DR: In this paper, an enhanced ZT value as high as 1.1 at ∼550 °C has been achieved in n-type nanostructured CoSb3−xTex skutterudite compounds through additional substitution of IVB-group elements (Si, Ge, Sn, Pb) for Sb.
Abstract: An enhanced ZT value as high as 1.1 at ∼550 °C has been achieved in n-type nanostructured CoSb3−xTex skutterudite compounds through additional substitution of IVB-group elements (Si, Ge, Sn, Pb) for Sb. Particularly, Sn was found to be the most effective element to enhance the ZT value by extending the solubility limit of Te in CoSb3−xTex, which decreases thermal conductivity more significantly than electrical conductivity. The reduced thermal conductivity is confirmed by the Raman scattering measurement of CoSb2.86M0.02Te0.12 (M = Si, Ge, Sn, Pb), which shows that Ge and Sn enter into the Sb-site of CoSb3 and generate significant changes in the vibration modes, whereas Si and Pb are not likely to get into the lattice of CoSb3. Furthermore, nanostructure with fine grains and “nanodots” also contributes to the reduction of thermal conductivity.
TL;DR: The quality and production technology of grain-oriented electrical steel have been improved over the past 70 years as mentioned in this paper, and many mechanisms have been proposed for the reason why Goss texture develops selectively during the final annealing stage.
TL;DR: This paper investigates the possibilities of applying the random forests algorithm (RF) in machine fault diagnosis, and proposes a hybrid method combined with genetic algorithm to improve the classification accuracy.
Abstract: This paper investigates the possibilities of applying the random forests algorithm (RF) in machine fault diagnosis, and proposes a hybrid method combined with genetic algorithm to improve the classification accuracy. The proposed method is based on RF, a novel ensemble classifier which builds a number of decision trees to improve the single tree classifier. Although there are several existing techniques for faults diagnosis, the application research on RF is meaningful and necessary because of its fast execution speed, the characteristics of tree classifier, and high performance in machine faults diagnosis. The proposed method is demonstrated by a case study on induction motor fault diagnosis. Experimental results indicate the validity and reliability of RF-based diagnosis method.
TL;DR: In this paper, the crystal structure, electrical conductivity and oxygen desorption properties of BaCo 07 Fe 03− x Nb x O 3− δ (BCFN, x ǫ=0-02) were studied by X-ray diffraction (XRD), different thermal analysis (DTA), four-terminal direct current conductivity (CCC) and oxygen temperature programmed deorption (O 2 -TPD), respectively.
TL;DR: In this article, the micelles formed by the aniline monomer in aqueous solution serve as a soft template for forming hollow spheres at the initial stage, and these hollow spheres are linearly aggregated and elongated to form short and long tubes.
Abstract: PANI nanotubes with diameters of 100-150 nm with conductivities of single nanotubes as high as 30.6 S . cm(-1) were directly oxidized with APS in the absence of hard templates and acidic dopants. The high conductivity was shown to result from protons produced during the polymerization. The pH decreases with increasing polymerization time, and the morphology changes from hollow spheres to short and long tubes. It is proposed that the micelles formed by the aniline monomer in aqueous solution serve as a soft template for forming hollow spheres at the initial stage. As the polymerization proceeds, these hollow spheres are linearly aggregated and elongated to form short and long tubes.
TL;DR: In this paper, a three-dimensional model was used to analyze the effect of the design parameters in the bipolar plates, including the number of flow channel bends, number of serpentine flow channels and the flow channel width ratio, on the cell performance of miniature PEMFCs.
TL;DR: In this paper, the electrochemical behavior of the Mn(II)/Mn(III) couple on carbon felt and spectral pure graphite were investigated by cyclic voltammetry, steady polarization curve, electrochemical impedance spectroscopy, transient potential-step experiment, X-ray diffraction and charge-discharge experiments.
TL;DR: In this article, large-scale CeO2 hierarchical architectures composed of well-aligned nanorods were controllably prepared through a simple Na3PO4 assisted hydrothermal reaction without any templates.
Abstract: Large-scale CeO2 hierarchical architectures composed of well-aligned nanorods were controllably prepared through a simple Na3PO4 assisted hydrothermal reaction without any templates. The products were characterized with X-ray diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. It was found that the CeO2 architectures are in flower-like and vertically aligned nanorod morphologies and composed of numerous fluorite cubic single-crystalline nanorods of 20−40 nm in diameter and lengths of up to several micrometers. The possible mechanism for the nanostructures formation was discussed.
TL;DR: It is proved that frequent itemsets, including representative item and having the same supports as representative item, can be identified directly by connecting the representative item with all the combinations of items in its subsume index, so the cost for processing this kind of itemsets is lowered, and the efficiency is improved.
Abstract: Efficient algorithms for mining frequent itemsets are crucial for mining association rules as well as for many other data mining tasks. Methods for mining frequent itemsets have been implemented using a BitTable structure. BitTableFI is such a recently proposed efficient BitTable-based algorithm, which exploits BitTable both horizontally and vertically. Although making use of efficient bit wise operations, BitTableFI still may suffer from the high cost of candidate generation and test. To address this problem, a new algorithm Index-BitTableFI is proposed. Index-BitTableFI also uses BitTable horizontally and vertically. To make use of BitTable horizontally, index array and the corresponding computing method are proposed. By computing the subsume index, those itemsets that co-occurrence with representative item can be identified quickly by using breadth-first search at one time. Then, for the resulting itemsets generated through the index array, depth-first search strategy is used to generate all other frequent itemsets. Thus, the hybrid search is implemented, and the search space is reduced greatly. The advantages of the proposed methods are as follows. On the one hand, the redundant operations on intersection of tidsets and frequency-checking can be avoided greatly; On the other hand, it is proved that frequent itemsets, including representative item and having the same supports as representative item, can be identified directly by connecting the representative item with all the combinations of items in its subsume index. Thus, the cost for processing this kind of itemsets is lowered, and the efficiency is improved. Experimental results show that the proposed algorithm is efficient especially for dense datasets.