Showing papers by "University of Science and Technology Beijing published in 2004"
TL;DR: A review of recent progress in the synthesis and characterization of polar-surface-induced ZnO nanostructures, their growth mechanisms, and possible applications as sensors, transducers, and resonators can be found in this article.
Abstract: Zinc oxide, an important semiconducting and piezoelectric material, has three key characteristics. First, it is a semiconductor, with a direct bandgap of 3.37 eV and a large excitation binding energy (60 meV), and exhibits near-UV emission and transparent conductivity. Secondly, due to its non-centrosymmetric symmetry, it is piezoelectric, which is a key phenomenon in building electro-mechanical coupled sensors and transducers. Finally, ZnO is bio-safe and bio-compatible, and can be used for biomedical applications without coating. With these unique advantages, ZnO is one of the most important nanomaterials for integration with microsystems and biotechnology. Structurally, due to the three types of fastest growth directions— , , and —as well as the ±(0001) polar surfaces, a diverse group of ZnO nanostructures have been grown in our laboratory. These include nanocombs, nanosaws, nanosprings, nanorings, nanobows, and nanopropellers. This article reviews our recent progress in the synthesis and characterization of polar-surface-induced ZnO nanostructures, their growth mechanisms, and possible applications as sensors, transducers, and resonators. It is suggested that ZnO could be the next most important nanomaterial after carbon nanotubes.
558 citations
TL;DR: It is shown that a disease free equilibrium point is globally stable if no endemic equilibrium point exists and the endemic point (if it exists) is global stable with respect to the whole state space except the neighborhood of the disease free state.
169 citations
TL;DR: In this paper, the size and shape of monodispersed CuO nanocrystals are controlled by the precipitation pyrolysis method by controlling the starting materials, reactive concentration and annealing temperature.
Abstract: Controlling the size, shape and structure of nanocrystals is technologically important because of the strong effect of size and shape on optical, electrical, and catalytic properties. Monodispersed nanocrystals of copper oxide were prepared by the precipitation?pyrolysis method. By controlling the starting materials, reactive concentration and annealing temperature, we can obtain spherical monodispersed CuO nanocrystals of different sizes or rodlike CuO nanocrystals. The particle sizes of CuO monodispersed nanocrystals can be tuned in the range between and 30?nm. The products have been characterized by x-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and the UV?visible absorption spectrum. The absorption spectra of CuO nanocrystals show clear evidence of the quantum size effect. The possible formation mechanism of monodispersed CuO nanocrystals is discussed.
165 citations
TL;DR: In this paper, a new Geographic Information Systems (GIS) grid-based three-dimensional deterministic model and taking the slope unit as the mapping unit were used to map landslide hazard using the 3-D safety factor index and failure probability.
Abstract: Based on a new Geographic Information Systems (GIS) grid-based three-dimensional (3-D) deterministic model and taking the slope unit as the mapping unit, this study maps landslide hazard using the 3-D safety factor index and failure probability. Assuming the initial slip to be the lower part of an ellipsoid, the 3-D critical slip surface in the 3-D slope stability analysis is located by minimizing the 3-D safety factor using the Monte Carlo random simulation. The failure probability of the landslide is calculated using an approximate method in which the distributions of c, φ and the 3-D safety factor are assumed to be in normal distribution. The method has been applied to a case study on three-dimensionally and probabilistically mapping landslide hazard.
135 citations
TL;DR: In this article, the twin orientations in channel die compression tests were determined by means of X-ray diffraction and EBSD technique in two samples of magnesium alloy AZ31 with different initial textures.
118 citations
TL;DR: In this article, the composition of the Ce conversion coating was investigated using X-ray photoelectron spectroscopy (XPS) and it was revealed that the coating predominately consisted of three-valent state cerium compound.
109 citations
13 Dec 2004
TL;DR: The paper discusses the edge-based ear recognition method including ear edge detection, ear description and feature extraction, recognition method and ear database construction.
Abstract: Application and research of ear recognition technology is a new subject in the field of biometric recognition The earlier research has shown that human ear is one of the representative human biometrics with uniqueness and stability The paper discusses the edge-based ear recognition method including ear edge detection, ear description and feature extraction, recognition method and ear database construction The feature vector is composed of the shape feature vector of the outer ear and the structural feature vector of the inner ear The local feature vectors are proved to be invariant to ear image's parallel move, scale and rotation.
105 citations
TL;DR: In this paper, a consistent thermodynamic data set for the Ti-B binary system was obtained by means of CALPHAD technology, where the sublattice model was used to describe the solid solution phases.
89 citations
TL;DR: In this article, a nano-crystalline MgO coating was formed on the surface of LiCoO 2 particle via a sol-gel method, which can improve the cycling stability of LiCOO 2 significantly.
86 citations
TL;DR: In this paper, the coarsening kinetics of gamma prime and age-hardening behavior have been investigated in a newly developed nickel base superalloy aged at elevated temperatures for times of up to 4000 h.
85 citations
TL;DR: In this article, the influence of discrete texture components and combinations of them on the earing behavior of aluminium during cup drawing was systematically investigated using the texture component crystal plasticity finite element method.
TL;DR: In this article, the hydrogen absorption/desorption (A/D) kinetics of hydrogen storage alloys Mg2−xAgxNi (x=0.05, 0.1) prepared by hydriding combustion synthesis in two-phase (α-β) region in the temperature range of 523-573 K have been investigated.
TL;DR: In this article, the effect of boron content on the processing for Fe-6.5-wt% Si alloy was studied, and thin sheets with a final thickness of 0.28-0.30mm were successfully fabricated using a conventional rolling process.
TL;DR: Inconel 740 with and without Na2SO4 deposit were oxidized in still air between 850 and 1000 °C to investigate the oxidation and hot corrosion behavior by means of XRD, SEM and EDS.
Abstract: The new nickel-based superalloy, Inconel 740, with and without Na2SO4 deposit were oxidized in still air between 850 and 1000 °C to investigate the oxidation and hot corrosion behavior by means of XRD, SEM and EDS. The kinetic curves of the alloy oxidized at 950 °C without Na2SO4 deposit and at 850 °C with Na2SO4 deposit obeyed the parabolic law, whereas, the uniform parabolic growth behavior of oxide was not followed at 1000 °C without Na2SO4 deposit and at 950 °C with Na2SO4 deposit due to oxide spallation at 1000 °C and the evaporation of Na2CrO4 melt at 950 °C, respectively. The oxide scales consisted of Cr2O3, (Ni,Co)Cr2O4, TiO2, Al2O3 and internal oxides at all temperatures. The internal sulfidation took place due to the existence of Na2SO4 deposit. The complex layered structure of oxide scales was in favor of the resistance to oxidation. The deposition of Na2SO4 accelerated the oxidation of the alloy and the degradation of corrosion resistance of alloy with Na2SO4 deposit was attributed to the dissolution of Cr2O3 induced by basic fluxing in molten Na2SO4.
TL;DR: In this article, an integrated infinite slope analysis model has been developed to evaluate the influence of infiltration on surficial stability of slopes by the limit equilibrium method, and a time-space based approach has been implemented to map the distributed landslide hazard in a GIS (Geographic Information Systems) and evaluate the shallow slope failure induced by a particular rainfall event that accounts for the rainfall intensity and duration.
Abstract: A rainfall-induced shallow landslide is a major hazard in mountainous terrain, but a time-space based approach is still an unsettled issue for mapping rainfall-induced shallow landslide hazards. Rain induces a rise of the groundwater level and an increase in pore water pressure that results in slope failures. In this study, an integrated infinite slope analysis model has been developed to evaluate the influence of infiltration on surficial stability of slopes by the limit equilibrium method. Based on this new integrated infinite slope analysis model, a time-space based approach has been implemented to map the distributed landslide hazard in a GIS (Geographic Information Systems) and to evaluate the shallow slope failure induced by a particular rainfall event that accounts for the rainfall intensity and duration. The case study results in a comprehensive time-space landslide hazard map that illustrates the change of the safety factor and the depth of the wetting front over time.
TL;DR: In this paper, the effect of Si content on dry sliding wear of spray-deposited Al-Si alloy was associated with applied loads, and it was found that with increasing Si content, the wear rate of the alloy decreased.
TL;DR: In this article, the authors present a fundamental concept of thermal comfort and acceptability, new air-conditioning strategies by using fluctuating air movement based on the findings of human responses to transient thermal environment, and a prediction of energy saving caused by elevated indoor temperature settings.
TL;DR: In this article, the conductivity at room temperature and the variation of conductivity with temperature in 80-280 K was measured for HCl-doped and DBSA-doping polyanilines.
04 Dec 2004
TL;DR: In this article, the authors considered an anisotropic swarm model with an attraction/repulsion function and studied its aggregation properties, showing that the swarm members will aggregate and eventually form a cohesive cluster of finite size around the swarm center.
Abstract: In this paper, we consider an anisotropic swarm model with an attraction/repulsion function and study its aggregation properties It is shown that the swarm members will aggregate and eventually form a cohesive cluster of finite size around the swarm center We also study the swarm cohesiveness when the motion of each agent is a combination of the inter-individual interactions and the interaction of the agent with external environment Moreover, we extend our results to more general attraction/repulsion functions The model in this paper is more general than isotropic swarms and our results provide further insight into the effect of the interaction pattern on individual motion in a swarm system.
TL;DR: In this paper, an acetate derived barium titanate gel was prepared and the phase developments were investigated by an in situ XRD technique at elevated temperatures in air and in O 2, XPS and Raman spectrum measurements.
TL;DR: The DMol cluster method based on density-functional theory has been employed to study the structural stability and electronic structure of La(n) (n=2-14) clusters and the results show strong odd-even alternation and that 7- and 13-atom clusters are magic.
Abstract: The DMol cluster method based on density-functional theory has been employed to study the structural stability and electronic structure of Lan (n=2–14) clusters. The ground states have been found out for lanthanum clusters. The Jahn-Teller effect plays an important role in this process because there are many isomers near the ground state. The magnetism is not sensitive to interatomic spacing when the change of interatomic spacing is in a small range. Lanthanum clusters grow in an icosahedral pattern. The results of the mean binding energy, of the second derivative of binding energy, and of the formation energy show strong odd–even alternation and that 7- and 13-atom clusters are magic. Further, the HOMO-LUMO gap, the mean nearest bond lengths, and the mean magnetic moments suggest that the convergence to bulk is slow and it shows an oscillatory behavior for small lanthanum clusters.
15 Sep 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors used in situ synthesis technology was adopted to fabricate SiC reinforced Ti 3 SiC 2 composite by displacement reaction of Si and TiC powders.
Abstract: In situ synthesis technology was adopted to fabricate SiC reinforced Ti 3 SiC 2 composite by displacement reaction of Si and TiC powders. The formation of SiC particles as reinforcements with elongated or equiaxed shape distributed in Ti 3 SiC 2 matrix. The average size of SiC equiaxed particles was about 2 μm and that of elongated ones was in the range of 5–8 μm in length and 2 μm in width. TiC with about 1 μm in size was also found in the composite. The particles of SiC or TiC inhibited the grain-boundary migration of Ti 3 SiC 2 resulting in a fine Ti 3 SiC 2 matrix with a grain size of 10 μm. Differential scanning calorimetry showed that Si reacted drastically with TiC at 1340 °C with release of heat. The presence of TiC in the Ti 3 SiC 2 /SiC composite should be attributed to decomposition of Ti 3 SiC 2 at 1500 °C rather than the loss of Si during reaction process that resulted in unreacted TiC left. Reaction paths in the present experiment were postulated on the basis of Ti–Si–C system and reaction model of Mo 2 C–Si to understand the mechanism of the formation of Ti 3 SiC 2 and SiC.
TL;DR: In this paper, the influence of the initial hydrogen pressure on the hydriding kinetics in the two-phase (α-β) region of the Mg2−xAlxNi (x=0,0.1) alloys was investigated.
TL;DR: In this paper, a new Monte Carlo random simulation method was proposed to identify the 3D critical slip surface of a slope, in which assuming the initial slip as the lower part of an ellipsoid and the slope stability analysis is based on a column-based three-dimensional slope stability model, a new geographic information systems (GIS) grid-based 3D deterministic model has been developed to calculate the threeD safety factor.
TL;DR: In this article, the hydrogen absorption/desorption (A/D) kinetics of hydrogen storage alloys Mg1.9Al0.1Ni prepared by hydriding combustion synthesis in two-phase (α-β) region in the temperature range from 523 to 573 K were investigated.
Abstract: The hydrogen absorption/desorption (A/D) kinetics of hydrogen storage alloys Mg1.9Al0.1Ni prepared by hydriding combustion synthesis in two-phase (α-β) region in the temperature range from 523 to 573 K have been investigated. The hydriding/dehydriding (H/D) reaction rate constants were extracted from the time-dependent A/D curves. The obtained hydrogen A/D kinetic curves were fitted using various rate equations to reveal the mechanism of the H/D processes. The relationships of rate constant with temperature were established. It was found that the three-dimensional diffusion process dominated the hydrogen A/D. The activation energies of Mg1.9Al0.1Ni are 52 ± 2 and 48 ± 1 kJ/mol H2 for the H/D processes smaller than that of Mg2Ni, which can be explained that the improvement of H/D reaction kinetics in Mg2Ni by using additive Al.
TL;DR: In this article, a simplified one-dimensional bioheat transfer model of cylindrical living tissues in the steady state has been set up for application in limb and whole body heat transfer studies, and its corresponding analytic solution has been derived in this paper.
Abstract: Based on the Pennes’ bioheat transfer equation, a simplified one-dimensional bioheat transfer model of the cylindrical living tissues in the steady state has been set up for application in limb and whole body heat transfer studies, and by using the Bessel’s equation, its corresponding analytic solution has been derived in this paper. With the obtained analytic solution, the effects of the thermal conductivity, the blood perfusion, the metabolic heat generation, and the coefficient of heat transfer on the temperature distribution in living tissues are analyzed. The results show that the derived analytic solution is useful to easily and accurately study the thermal behavior of the biological system, and can be extended to such applications as parameter measurement, temperature field reconstruction and clinical treatment.
TL;DR: In this paper, the phase diagram and thermodynamic properties of the Ni-Ga system are assessed based on the CALPHAD approach, using all available experimental data and applying appropriate thermodynamic models.
Abstract: Phase diagram and thermodynamic properties of the Ni-Ga system are assessed based on the CALPHAD approach, using all available experimental data and applying appropriate thermodynamic models. The liquid phase and the Ni-based solid solution (Ni) are treated as disordered solutions. The thermodynamic behavior of the ordered intermetallic compounds with appreciable ranges of homogeneity, Ni3Ga and NiGa, are described by a two-sublattice model, and the order-disorder transformation between Ni3Ga and fcc-(Ni) is also explicitly considered in this work. The other five intermetallic compounds are treated as stoichiometric line compounds. The phase diagram and the thermodynamic properties calculated from the optimized model parameters are in good agreement with most of the experimental data.
TL;DR: A chemical investigation of the Orchidaceae Arundina gramnifolia has led to the isolation of a novel stilbenoid, named arundinan, which has been elucidated as 2-hydroxybenzyl)-3-Hydroxy-5-methoxybibenzyl on the basis of physical and chemical evidence and spectral analysis.
TL;DR: In this article, the intermolecular attraction of soil to solid materials is derived from Lifishitz's intermolescular attraction theory between two macro-objects, which can more effectively reveal the rules of soil adhesion when the contact angle of water on the solid materials surface changes from 0 to 180°.
TL;DR: In this paper, the change in crystallinity during rolling deformation and heating is analyzed in terms of X-ray data (peaks and background) that are integrated over the entire pole sphere.