Aspect graphs: An introduction and survey of recent results

The study of the aspect graph of a three-dimensional object has recently become an active area of research in computer vision. The aspect graph provides a complete enumeration of all possible distinct views of an object, given a model for viewpoint space and a definition for “distinct.” This article presents a tutorial introduction to the aspect graph, surveys the current state of the art in algorithms for automatically constructing aspect graphs, and describes some possible applications of aspect graphs in computer vision and computer graphics.     

High temperature studies of Fe-Mn-Al-C alloys with different manganese concentrations in air and nitrogen

The formation of AIN was studied using a series of Fe-Mn-Al-C alloys with manganese contents from 20 to 40 wt%. All investigations were carried out in air and nitrogen at 1000° C. The permeability (D _N N _N) of nitrogen in Fe-Mn-Al-C alloys was found to be a major factor influencing the formation of AIN precipitates which are always observed underneath the oxide scales of the specimen. The formation of AIN is related to the lower formation rate of Al₂O₃ and high permeability of nitrogen; therefore AIN can only be formed in those alloys with a higher manganese concentration because the specimens are treated in air and in pure nitrogen at 1000 C.     

Mass transport studies of different additives in polyamide and exfoliated nanocomposite polyamide films for food industry

The development of new food packaging films through the incorporation of nanoparticles, and the effect of the nanoparticles on the process of migration of the substances used in manufacturing the new films is expected to lead to an improvement in the shelf life of food and thus, consumer safety and health. In recent years, attention has focused on nanocomposites because these compounds often exhibit unexpected hybrid properties derived from synergistic reactions between nanoparticles and the polymeric matrix. The exfoliation of nanoclays in polyamide film provides a film with better barrier properties than that obtained through the intercalation of nanoclays. Migration of chemicals from food packaging into food may produce potential adverse health effects because of exposure to toxic compounds. The present study addressed the migration of caprolactam, 5‐Chloro‐2‐(2,4‐dichlorophenoxy)phenol (triclosan) and trans,trans‐1,4‐diphenyl‐1,3‐butadiene (DPBD) from polyamide and polyamide‐nanoclays to different types of food simulants. The values for limit of detection (LOD) obtained for caprolactam, triclosan and DPBD was 0.5 mg/L, 0.02 mg/L and 0.01 mg/L, respectively. Furthermore, instrumental precision was evaluated through repeatability injections, resulting in relative standard deviations lower than 3.08%. Diffusion coefficients were calculated according to a mathematical model based on Fick's Second Law, and the results were discussed in terms of the parameters that may have the greatest effect on migration. The presence of polymer nanoparticles was found to slow down the rate of migration of substances from the matrix polymer into the food up to six times. Copyright © 2009 John Wiley & Sons, Ltd.     

Discoloration mechanism,structures and recent applications of thermochromic materials via different methods: A review

Thermochromic material is a kind of smart material whose color will vary as the result of the phase transition caused by the temperature change. The characteristics of thermochromic materials are the memory functions to the temperature, having great potential applications in aerospace, military, anti-counterfeiting technology, construction and other fields. In recent years, many kinds of thermochromic materials have been prepared by different methods and their discoloration mechanisms are various according to published literatures. In this paper, the classification, discoloration mechanism, preparation methods, application fields and development trend of thermochromic materials are reviewed.     

Laser applications to chemical and environmental analysis: an introduction

This issue of Applied Optics features papers on the application of laser technology to chemical and environmental analysis. Many of the contributions to this issue, although not all, result from papers presented at the 1996 OSA Topical Meeting on Laser Applications to Chemical and Environmental Analysis, which was held in Orlando, Florida, in March 1996. This successful meeting, with nearly 100 participants, continued the tradition of earlier Laser Applications to Chemical Analysis (LACA) meetings. The title change reflects an expended scope and an even greater emphasis on environmental analysis than the previous four LACA meetings.     

Antifouling nanocomposite polymer coatings for marine applications:A review on experiments,mechanisms, and theoretical studies

Marine fouling is a worldwide challenge with huge damages on industrial structures, side effects on economics of industries, and environmental and safety-related hazards. Different approaches have been used for combating fouling in the marine environment. Meanwhile, nanocomposite polymer coatings are a novel generation of antifouling coatings with merits of toxin-free chemical composition and ease of large-scale application. Nanomaterials such as nano-metals, nano-metal oxides, metal-organic fra...     

混凝土中钢筋锈蚀电化学测量方法的介绍

混凝土中的钢筋锈蚀为电化学腐蚀,可用电位-pH图来描述钢筋在不同体系下的稳定性.传统方法测定钢筋锈蚀的时间太长,而阳极电位法只能对锈蚀作定性判断.介绍了混凝土中钢筋锈蚀的3种电化学测试方法,并通过测试表明:根据线性极化法测得的腐蚀电流可以计算钢筋的锈蚀速度;交流阻抗法能反映混凝土中钢筋锈蚀的动力学过程,并得到相应的等效电路;用Mott-Schottkv方法表明钢筋钝化膜为载流子浓度在1026m-3数量级的n型半导体.     

Electrochemical and microstructural studies of sintered and sintered-plasma nitrided steel containing different alloying elements

The corrosion of sintered and sintered-plasma nitrided steels containing different alloying elements was evaluated through analysis of the potentiodynamic polarization curves of the samples at pH = 7, with 1.25 M KNO₃ as electrolyte. The Fe-3.0% Ni and Fe-0.1% C sintered alloys show better performance in relation to electrochemical corrosion, than sintered pure iron samples. In addition, Fe-4.0% Mn, Fe-1.5% Mo and Fe-1.5% Si alloys exhibited increased anodic current densities in relation to the pure iron sample. After the nitriding process the anodic current densities of all samples containing an alloying element were considerably diminished. The sintered-nitrided pure iron sample was the only nitrided part whose current density was higher than the current density of the non-nitrided sample.     

Inspection procedures in manufacturing processes: recent studies and research perspectives

Quality inspections are performed in almost every production system to prevent nonconforming products from reaching final customers or end users. Quality inspections are typically performed referring to specific inspection procedures, depending on the production process. Two general inspection paradigms may be identified: online inspection and offline inspection. These are differentiated by the way in which inspections are made. The paper presents a recent survey on new studies on inspection procedures for both paradigms. The main novelty of the study is the identification of new research perspectives in such a highly explored field. New schemes of analysis allow highlighting the research areas which are not adequately covered by the literature. A brief examination of some bibliometric aspects is also proposed.     

Equilibrium and kinetic studies in adsorption of heavy metals using biosorbent: a summary of recent studies

Distinctive adsorption equilibria and kinetic models are of extensive use in explaining the biosorption of heavy metals, denoting the need to highlight and summarize their essential issues, which is the main purpose of this paper. As a general trend, up until now, most studies on the biosorption of heavy metal ions by miscellaneous biosorbent types have been directed toward the uptake of single metal in preference to multicomponent systems. In particular, Langmuir and Freundlich models are the most common isotherms for correlating biosorption experimental data though other isotherms, which were initially established for gas phase applications, can also be extended onto biosorption system. In kinetic modeling, the pseudo-first and -second order equations are considered as the most celebrated models.     

Hydrogen detection in metals: a review and introduction of a Kelvin probe approach

Abstract

Hydrogen in materials is an important topic for many research fields in materials science. Hence in the past quite a number of different techniques for determining the amount of hydrogen in materials and for measuring hydrogen permeation through them have been developed. Some of these methods have found widespread application. But for many problems the achievable sensitivity is usually not high enough and ready-to-use techniques providing also good spatial resolution, especially in the submicron range, are very limited, and mostly not suitable for widespread application. In this work this situation will be briefly reviewed and a novel scanning probe technique based method introduced.     

The use of QCA in science,technology and innovation studies: a review of the literature and an empirical application to knowledge transfer

This article analyses the use of qualitative comparative analysis (QCA) in social studies on science, technology and innovation. The goals are to address how and why the method is used, and to explore the advantages and shortcomings for this research area. A review of the literature and practical application are combined. Firstly, the article finds that the acceptance of QCA is unevenly distributed in the major research fields related to knowledge production. It is used mainly to study innovation in firms but is largely absent in science and technology studies. Second, an original study on university–industry links provides a strategic site that displays how research unfolds. Its findings demonstrate the combinations of factors that shape knowledge transfer and the configurational nature of the process. The article offers an account of challenges and directions for future research and discusses the possibilities of the method as a third way between qualitative and quantitative traditions in science, technology and innovation.

     

Transition-metal substitution in PbAlBO4: Synthesis,structural and spectroscopic studies of manganese containing phases

Mullite-type metal borates PbAlBO₄ with planar BO₃ groups are potential candidates for nonlinear optical properties. We successively substituted aluminum with manganese in the composition PbAl_1?xMn_xBO₄, which would help tuning the crystal chemistry and related physical properties. The end member PbAlBO₄ was synthesized by conventional solid state reaction; the other members of the PbAl_1?xMn_xBO₄ series were prepared by glycerin method. The fundamental parameter approach was applied in the Rietveld refinements to describe the X-ray powder diffraction profiles. The cell parameters and interatomic bond distances were studied with respect to the chemical composition x. The MO₆ octahedral distortion linearly increased with the averaged MO bond distance, which is correlated with the increasing amount of manganese atoms in the structure. The change of the average crystal size and microstrain were explained in terms of Al/Mn ratio in the solid solution. While the empirical bond-valence sums (BVS) of one oxygen atom, bridging the edge-sharing MO₆ octahedron, were found to be under-bonded, the other one was over-bonded. The stereoactivity of the 6s² lone electron pair of the Pb²⁺ cation was characterized in terms of the absolute value of eccentricity parameter (|Φ_i|). Both bond valence parameter (r_0i) and BVS of Pb showed a linear correlation with |Φ_i|. Deconvolution of the absorption feature of the infrared powder spectra between 1000 cm^?1 and 1400 cm^?1 required four fitted bands, which were assigned to BO stretching vibrations of the trigonal planar BO₃ groups. With increasing Al³⁺ dilution in PbAl_1?xMn_xBO₄ almost all observed modes shifted toward lower wavenumbers confirming the solid solution. The absorptions caused by the vibrations of the heavy atom Pb were observed in the far-IR region.     

Electrochemical and morphological studies of an electroactive material derived from 3-hydroxyphenylacetic acid: a new matrix for oligonucleotide hybridization

This paper describes the formation of polymeric films derived from 3-hydroxyphenylacetic acid electropolymerized onto graphite electrodes through cyclic voltammetry. We observed the formation of an electroactive material over the electrode surface. The modified electrode showed significant blocking behavior to electron transfer reaction of the pair redox ferricyanide/ferrocyanide, indicating repulsion electrostatic with the negatively charged carboxylate groups of the polymer. The quasi-reversible behavior to Ru(NH₃)₆Cl₂ suggests electrostatic attraction, facilitating the charge transfer. The modified electrode was studied through electrochemical quartz crystal microbalance, electrochemical impedance spectroscopy, and atomic force microscopy. These analyses indicate modification of the graphite electrode. Surface analysis by AFM showed that the morphology of the modified electrode surface presents globular form, randomly distributed, and formed by lower globules with diameter near 100 nm. Immobilization and hybridization of oligonucleotide onto the modified electrode were successfully carried out by using both direct electrochemical oxidation of nitrogenated bases and the redox electroactive indicator methylene blue.     

Piezoresponse force microscopy and recent advances in nanoscale studies of ferroelectrics

In this paper, we review recent advances in piezoresponse force microscopy (PFM) with respect to nanoscale ferroelectric research, summarize the basic principles of PFM, illustrate what information can be obtained from PFM experiments and delineate the limitations of PFM signal interpretation relevant to quantitative imaging of a broad range of piezoelectrically active materials. Particular attention is given to orientational PFM imaging and data interpretation as well as to electromechanics and kinetics of nanoscale ferroelectric switching in PFM.     

Recent advances on understanding the origin of superhardness in nanocomposite coatings: A critical review

The remarkable mechanical properties of nanocomposite coatings, such as superhardness, high elastic modulus and recovery, excellent resistance against cracking, low wear rate, and high thermal stability, are due to their unique structures and deformation mechanisms at the nanometer scale. In this paper, recent advances are reviewed mainly with respect to the understanding of the origin of superhardness in nanocomposite coatings. A few controversial issues relevant to the identification of superhard coatings are mentioned. Also discussed are several models, based on analyses and simulations at different levels from continuum to atomistic scales, to elucidate likely superhardening mechanisms. Finally, some open problems and continuing challenges are highlighted.     

Two-dimensional photocatalyst design: A critical review of recent experimental and computational advances

In recent years, two-dimensional (2D) semiconductor photocatalysts have been widely applied in water splitting, CO₂ reduction, N₂ fixation, as well as many other important photoreactions. Photocatalysts in the form of 2D nanosheet possess many inherent advantages over traditional 3D nanopowder photocatalysts, including improved light absorption characteristics, shorter electron and hole migration paths to the photocatalysts’ surface (thus minimizing undesirable electron-hole pair recombination), and abundant surface defects which allow band gap modulation and facilitate charge transfer from the semiconductor to adsorbates. When synergistically exploited and optimized, these advantages can impart 2D photocatalysts with remarkable activities relative to their 3D counterparts. Accordingly, a wide range of experimental approaches is now being explored for the synthesis of 2D photocatalysts, with computational methods increasingly being used for identification of promising new 2D photocatalytic materials. Herein, we critically review recent literatures related to 2D photocatalyst development and design. Particular emphasis is placed on 2D photocatalyst synthesis and the importance of computational studies for the fundamental understanding of 2D photocatalyst electronic structure, band gap structure, charge carrier mobility and reaction pathways. We also explore the practical challenges of using 2D photocatalysts, such as their difficulty to synthesize in large quantity and also their characterization. The overarching aim of this review is to provide a snapshot of recent work targeting high-performance 2D photocatalysts for efficient solar energy conversion, thus laying a firm base for future advancements in this rapidly expanding area of photocatalysis research.