Block truncation coding with color clumps: A novel feature extraction technique for content based image classification

The paper has explored principle of block truncation coding (BTC) as a means to perform feature extraction for content based image classification. A variation of block truncation coding, named BTC with color clumps has been implemented in this work to generate feature vectors. Classification performance with the proposed technique of feature extraction has been compared to existing techniques. Two widely used public dataset named Wang dataset and Caltech dataset have been used for analyses and comparisons of classification performances based on four different metrics. The study has established BTC with color clumps as an effective alternative for feature extraction compared to existing methods. The experiments were carried out in RGB color space. Two different categories of classifiers viz. K Nearest Neighbor (KNN) Classifier and RIDOR Classifier were used to measure the classification performances. A paired t test was conducted to establish the statistical significance of the findings. Evaluation of classifier algorithms were done in receiver operating characteristic (ROC) space.     

Spatially resolved electron energy-loss studies of metal–ceramic interfaces in transition metal/alumina cermets

Composites consisting of an alumina matrix and 20 vol.% transition metal (Ni or Fe) particles, prepared by hot pressing powder blends, have been studied using spatially resolved transmission electron energy-loss spectroscopy (EELS), and, to a lesser extent, by high-resolution electron microscopy (HREM). Particular attention was paid to the elucidation of the chemical bonding mechanisms at the metal-ceramic interface; EELS spectra from interfacial regions being obtained via a spatial difference technique. From both qualitative and quantitative interpretation of EELS near-edge structures, as well as observed HREM images, the data appear to be consistent with the presence of an Al-terminated alumina at the interface and the formation of direct transition metal – aluminium bonds in Al(O₃M) (M = Ni or Fe) tetrahedral units, possibly as a result of the dissolution and interfacial reprecipitation of Al during processing. These results correlate well with similar model studies on diffusion-bonded Nb/Al₂O₃ interfaces and may, in the light of recent theoretical electronic structure calculations, have implications for the resultant interfacial bond strength in such materials.     

High-resolution imaging of organic pharmaceutical crystals by transmission electron microscopy and scanning moiré fringes

Formulation processing of organic crystalline compounds can have a significant effect on drug properties, such as dissolution rate or tablet strength/hardness. Transmission electron microscopy (TEM) has the potential to resolve the atomic lattice of these crystalline compounds and, for example, identify the defect density on a particular crystal face, provided that the sensitivity of these crystals to irradiation by high-energy electrons can be overcome. Here, we acquire high-resolution (HR) lattice images of the compound furosemide using two different methods: low-dose HRTEM and bright-field (BF) scanning TEM (STEM) scanning moiré fringes (SMFs). Before acquiring HRTEM images of furosemide, a model system of crocidolite (asbestos) was used to determine the electron flux/fluence limits of low-dose HR imaging for our scintillator-based, complementary metal-oxide semiconductor (CMOS) electron camera by testing a variety of electron flux and total electron fluence regimes. An electron flux of 10 e⁻/(Ų s) and total fluence of 10 e⁻/Ų was shown to provide sufficient contrast and signal-to-noise ratio to resolve 0.30 nm lattice spacings in crocidolite at 300 kV. These parameters were then used to image furosemide which has a critical electron fluence for damage of ≥10 e⁻/Ų at 300 kV. The resulting HRTEM image of a furosemide crystal shows only a small portion of the total crystal exhibiting lattice fringes, likely due to irradiation damage during acquisition close to the compound's critical fluence. BF-STEM SMF images of furosemide were acquired at a lower electron fluence (1.8 e⁻/Ų), while still indirectly resolving HR details of the (001) lattice. Several different SMFs were observed with minor variations in the size and angle, suggesting strain due to defects within the crystal. Overall BF-STEM SMFs appear to be more useful than BF-STEM or HRTEM (with a CMOS camera) for imaging the crystal lattice of very beam-sensitive materials since a lower electron fluence is required to reveal the lattice. BF-STEM SMFs may thus prove useful in improving the understanding of crystallization pathways in organic compounds, degradation in pharmaceutical formulations and the effect of defects on the dissolution rate of different crystal faces. Further work is, however, required to quantitatively determine properties such as the defect density or the amount of relative strain from a BF-STEM SMF image.     

Cu—Ti合金原位生成TiB2颗粒时的组织演变

通过原位生成反应,采用Cu-3．4％Ti和Cu-0．7％B中间合金,利用快速凝固技术制备纳米TiB,颗粒增强块体Cu—Ti合金,然后对合金在900℃进行热处理l～10h。高分辨透射电镜（HRTEM）观察表明,在铜熔体中,Ti和B通过原位反应生成初始纳米TiB2颗粒和TiB晶须,TiB晶须的生成会导致TiB2颗粒粗化。初始TiB2颗粒沿晶界分布,会阻碍晶粒在高温下的生长。在对合金进行热处理时,晶粒内的Ti和B原子通过扩散反应生成二次TiB2颗粒。对合金热处理前后的导电率和硬度进行测试。结果显示,生成的二次TiB2颗粒能够延缓合金在高温下硬度的下降,合金的电导率和硬度随着热处理时间的延长而增加,在处理8h时分别为33．5％IACS和HVl58。     

Electronic property investigations of single-walled carbon nanotube bundles in situ within a transmission electron microscope: an evaluation

We have evaluated a combined transmission electron microscopy (TEM)–scanning tunnelling microscopy (STM) (hence TEM-STM) sample holder for the investigation of the mechanical and electrical properties of individual bundles of single-walled carbon nanotubes (SWCNTs) together with their simultaneous observation, analysis and mechanical modification in the TEM. Current-voltage (I–V) measurements from bundles of SWCNTs were observed to change as the bundles were deformed both reversibly and irreversibly, although the observed behaviour was somewhat complex. Electron energy loss spectroscopy (EELS) analysis revealed measurable changes in the bonding of the carbon atoms within the graphene layers upon bundle deformation, with measurable changes in the π*/(π*+σ*) peak ratios observed at the carbon K-edge. Reversible deformation of the bundles was consistent with the sensitivity of σ bonding to deviations from nonplanarity, whereas irreversible deformation was consistent with the introduction of nonhexagonal defects into the graphene sheets.     

Oxygen K near-edge spectra of amorphous silicon suboxides

Chemical disorder in silicon suboxides has been modelled by constructing several small atomic clusters which were used as input for multiple scattering calculations of the energy-loss near-edge structure at the oxygen K-edge. A redistribution of intensity at the O K-edge is observed as the number of second neighbour oxygen atoms is reduced. Since photoelectrons scattered by second neighbours of oxygen (at least) contribute to the spectra, O K-edge data provide valuable structural information, additional to that obtained from the Si L₂₃-edge, which appears to be restricted to the local coordination shell. Comparison with the experimental O K-edge for a-SiO_x (O < × < 2), prepared by oxidation of amorphous Si, suggests that the material consists of an intimate mixture of a wide range of Si sites with varying proportions of oxygen and silicon in the first neighbour shell.