Carbon nanostructures with precisely controlled shapes are difficult materials to synthesize. A facet-selective-catalytic process was thus proposed to synthesize polymer-linked carbon nanostructures with different shapes, covering straight carbon nanofiber, carbon nano Y-junction, carbon nano-hexapus, and carbon nano-octopus. A thermal chemical vapor deposition process was applied to grow these multi-branched carbon nanostructures at temperatures lower than 350 °C. Cu nanoparticles were utilized as the catalyst and acetylene as the reaction gas. The growth of those multi-branched nanostructures was realized through the selective growth of polymer-like sheets on certain indexed facets of Cu catalyst. The vapor-facet-solid (VFS) mechanism, a new growth mode, has been proposed to interpret such a growth in the steps of formation, diffusion, and coupling of carbon-containing oligomers, as well as their final precipitation to form nanostructures on the selective Cu facets.

Ideal metallic glasses are the metallic glasses that satisfy electronic structure stability. Previously we have developed a so-called 'cluster-plus-glue-atom model' and more recently a 'cluster-resonance model' for the ideal metallic glasses. Good metallic glass forming compositions always satisfy simple cluster formulas [cluster] (glue atoms), with x denoting the number of glue atoms matching one cluster. In this paper we present an electrochemical potential equilibrium criterion based on these models to obtain the number of glue atoms. By examples of Cu-Zr and Co-B bulk metallic glasses, it is confirmed that the experimentally determined good BMG-forming compositions well agree with the calculated composition formulas.

This paper addresses the problem of affine distortions caused by viewpoint changes for the application of image retrieval. We study how to expand the visual words from a query image for better retrieval recall without the sacrifice of retrieval precision and efficiency. Our main contribution is the building of visual dictionaries that retain the mapping relationships between visual words extracted from different viewpoints of the same object. Additionally, in each mapping rule we record the affine transformation in which the two visual words are related, as a compact code of viewpoints relationships. By analogizing the concepts of verb stem and verb tense in text, we use Visual Stems to denote visual words extracted from robust local patches, and record the relationships between their affine variants as visual stem mapping rules, including the geometric relationships coded as Geometric Tenses. In this way, our method augments original visual vocabulary with sufficient and accurate expansion information. In query phase, only the objects corresponding to the same visual stems and coherent geometric tense codes will be regarded as similar ones. Moreover, the mapping rules can be learned offline with only one sample for each object. Experiments show that our method can support efficient object retrieval with high recall, requiring little extra time and space cost over traditional visual vocabularies.

Progressive transmission is very effective to reduce retrieval latency in mobile visual search. However, the acceleration effects of existing progressive transmission strategies are often limited because of the neglect of geometric information in the query image. This paper proposes an effective and efficient geometric context-preserving progressive transmission method, which is suitable for mobile visual search. Here a query image is divided into blocks and local features in the same block are used as query units rather than a single feature. Since clustered features with geometric information are more discriminative, only a few of them could support correct matching with high precision. Thus our method significantly decreases the number of features needed for transmission, and dramatically reduces the retrieval latency. Experiments on Stanford dataset for mobile visual search show that, with comparable precision, we uses 43% less retrieval time than existing progressive transmission method. Moreover, we establish and release a large-scale image dataset called MVSBench which is more difficult and suitable for mobile visual search. It contains 75500 images and considers many variations like view change, blur, scale, illumination and rotation. MVSBench is another major contribution of this paper, and our method also outperforms other strategies on this dataset.

Effects of ion bombardment on the growth of carbon nanomaterials on Fe substrates in microwave plasma chemical vapor deposition were investigated. The product morphologies are directly correlated with the kinetic energy of bombarding ions and range from nanosheets, through cones, to aligned nanotubes for bias voltages from 0to−250V, respectively. A change in growth mechanism from a base growth to tip growth induced by the competition between etching and growth is responsible for the observed changes. These findings bring insights into the growth mechanism and provide a strong tool to control the structure of carbon nanomaterials.

The formation of bulk metallic glasses (BMG) in the Cu-rich Cu–Zr–Ti ternary system is studied by using the ‘e/a-variant line criterion’. Three such lines, (Cu9Zr4)1−xTix, (Cu61.8Zr38.2)1−xTix and (Cu56Zr44)1−xTix, are defined in the Cu–Zr–Ti system by linking three binary compositions Cu9Zr4, Cu61.8Zr38.2 and Cu56Zr44 to the third element Ti. The binary compositions Cu9Zr4, Cu61.8Zr38.2 and Cu56Zr44 correspond to specific Cu–Zr binary clusters. BMGs are obtained by copper mould suction casting method with Ti contents of 7.5–15at.%, 7.5–12.5at.% and 5–12at.%, respectively along the (Cu9Zr4)1−x Tix, (Cu61.8Zr38.2)1−xTix and (Cu56Zr44)1−xTix lines. The BMGs on each composition line manifest decreased thermal stabilities and glass forming abilities (GFAs) with increasing Ti contents. The maximum GFA appears at Cu64Zr28.5Ti7.5, with characteristic thermal parameters of Tg=736K, Tx=769K, Tg/Tl=0.627 and γ=0.403, which are all superior to those reported for the known Cu60Zr30Ti10 BMG.

Compositions with high glass forming ability have been identified in Zr-Cu-Al system with the help of a thermodynamic parameter, which takes into account the enthalpy of chemical mixing (Delta H-chem), the mismatch entropy normalized by Boltzmann's constant (S-sigma/k(B)) and the configurational entropy (S-config/R). The best bulk metallic glass forming composition is identified as the one at Delta H-chem and S-sigma/k(B) maxima in a specific range of S-config/R. A product of thermodynamic parameters (Delta H-chem x S-sigma/k(B)) is found to have strong correlation with glass forming ability and can help to identify the exact composition that can form bulk metallic glass. (c) 2006 Elsevier Ltd. All rights reserved.

Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu-Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0.382)(100-x)Nb-x, where x=1.5 and 2.5 at. %, and (Cu0.618Zr0.382)(98)Sn-2. The present results may open a route to prepare amorphous alloys with improved glass forming ability. (c) 2006 American Institute of Physics.

The present paper investigates the formation and composition characteristics of Cu-based bulk metallic glasses (BMGs) in the inter-transition metal system Cu-Zr-Ti by using an “e/a-variant criterion” which is relevant to clusters. Three such composition lines, (Cu9/13Zr4/13)100-xTix, (Cu０.618Zr０.382)１００-xTix and (Cu０.56Zr０.4４)100-xTix, are defined in the Cu-Zr-Ti system. Among them, Cu９Zr4, Cu61.８Zr38.2 and Cu56Zr44 are specific Cu-Zr binary cluster compositions. Alloy compositions are designed along these three composition lines, and alloy rods with diameter of 3mm are prepared by copper mould casting. X-ray and TEM analysis show that BMGs are formed within Ti content range of x=7.5%—15%, x=7.5%—12.5% and x=5%—12% respectively along these three lines. Thermal analysis results further indicate that these BMGs have igher thermodynamic Tg,Tx,Tg/Tl and γ values, and these values of BMGs on every composition line decrease with increasing Ti content. The optimum BMG composition in this system is Cu64Zr28.５Ti7.5 on the (Cu９/13Zr4/13)１00-xTix series, which also has the highest hardness and activation energy of crystallization. The characteristic parameters of this BMG are Tg＝736K, Tx＝769K, Tg/Tl=0.627,γ=0.403, Hν= 6.74GPa and ΔE=3.88 eV, which are all superior to those of the reported BMG Cu6０Zr3０Ti１０.

Based on the cluster line criterion, the Ag addition into the Cu8Zr5 cluster composition is investigated for the search of ternary Cu–Zr–Ag bulk metallic glasses with high glass forming abilities. Two initial binary compositions Cu0.618Zr0.382 and Cu0.64Zr0.36 are selected. The former one corresponds to a deep eutectic point; it is also the composition of the Cu8Zr5 icosahedron, which is derived from the Cu8Zr3 structure. The latter one, which can be regarded as the Cu8Zr5 cluster plus a glue atom Cu, is the best glass-forming composition in the Cu–Zr binary system. Two composition lines (Cu0.618Zr0.382)1−xAgx and (Cu0.64Zr0.36)1−xAgx are thus constructed in the Cu–Zr–Ag system by linking these two compositions with the third constitute Ag. A series of Cu–Zr–Ag bulk metallic glasses are found with 2–8at.% Ag contents in both composition lines. The optimum composition (Cu0.618Zr0.382)0.92Ag0.08 within the searched region with the highest Tg/Tl=0.633, is located along the cluster line (Cu0.618Zr0.382)1−xAgx, where the deep eutectic Cu0.618Zr0.382 exactly corresponds to the dense packing cluster Cu8Zr5. The alloying mechanism is discussed in the light of atomic size and electron concentration factors.