Exact Low-Rank Matrix Completion from Sparsely Corrupted Entries Via Adaptive Outlier Pursuit

Recovering a low-rank matrix from some of its linear measurements is a popular problem in many areas of science and engineering. One special case of it is the matrix completion problem, where we need to reconstruct a low-rank matrix from incomplete samples of its entries. A lot of efficient algorithms have been proposed to solve this problem and they perform well when Gaussian noise with a small variance is added to the given data. But they can not deal with the sparse random-valued noise in the measurements. In this paper, we propose a robust method for recovering the low-rank matrix with adaptive outlier pursuit when part of the measurements are damaged by outliers. This method will detect the positions where the data is completely ruined and recover the matrix using correct measurements. Numerical experiments show the accuracy of noise detection and high performance of matrix completion for our algorithms compared with other algorithms.     

Nitric oxide reduction at noble metal electrodes: a voltammetric study in acid solution

Features of the electrochemical reduction of nitric oxide on platinum, palladium, rhodium and ruthenium in aqueous perchloric acid solutions (0.33–1.0 M) are compared. The results from voltammetric studies (ie linear potential sweep and rotating disc electrode) using the bulk metal electrodes are described and compared with residual current voltage plots in acid electrolyte alone. In general, three nitric oxide reduction peaks are observed on the metals. The most anodic peak, at ca E = 0.15 V vs sce is attributed to the one-electron reduction of nitric oxide to an adsorbed NOH intermediate on a bare metal surface (ie one free of oxides or adsorbed hydrogen). The other two peaks occur in potential regions where adsorbed hydrogen is present on the metal surface (ca E = 0.0 and −0.20 V, respectively). The co-adsorbed hydrogen complicates the analysis and precludes an unambiguous interpretation of these two peaks. However, they apparently reflect nitric oxide reduction to nitrogen, hydroxylamine and/or ammonia. In a cathodic scan on the rhodium electrode, a current plateau is seen instead of the first (most anodic) peak, a probable consequence of oxide film formation with subsequent chemical complications. On the ruthenium electrode the first two (most anodic) peaks are not observed probably due to a relatively stable oxide layer. Reaction selectivities at metal black gas diffusion cathodes operating in an electrogenerative (ie galvanic) mode with perchloric acid electrolyte are compared with the voltammetric results at the corresponding bulk electrodes. Dinitrogen formation is observed on the platinum and rhodium black electrodes as suggested from voltammetric results. A series-parallel reaction sequence is proposed to explain the results. Limitations of using simple voltammetric techniques for predicting behavior of large scale preparative electrochemical reactors are discussed.     

Nondestructive examination of epoxy adhesive-bonded structures exposed to a humid environment: A comparison of low- and high-frequency dielectric measurements

Broadband dielectric measurements (10 ?2 to 3 GHz) are reported on the effects of exposure of thick film adhesive-bonded structures to moisture. Measurement of the dielectric properties over a broad frequency range allows identification of water both in voids and as a molecular dispersion in the matrix. Changes in the low frequency region of the dielectric spectrum can be attributed to a combination of processes associated with plasticisation of the adhesive, interfacial polarisation effects, and hydration of the surface oxide layer. The data obtained are complemented by mechanical testing and failure analysis of the bond structure measured as a function of the time of exposure. This study indicates that for thick film adhesives the ageing characteristics are apparently independent of the surface treatment. In one of the joints studied an additional feature is identified which appears to correlate with the premature aging of the joint structure.     

Imaging large vessels using cosmic-ray muon energy-loss techniques

Imaging the internal structure of large vessels (2–20 m in diameter) is not possible with most traditional imaging methods. The sheer size renders gamma-ray and other high-energy photon, neutron, electrical and acoustic techniques useless, whilst the use of high-energy accelerators required to produce charged-particles of sufficient energy are impractical in most industrial situations. The use of naturally occurring high-energy (GeV) cosmic-ray mu-mesons (muons) provides an effective solution to the penetration problem. The problems of low intensity at near-horizontal angles with the cosmic-ray muon flux are addressed by using energy-loss imaging methods. In other methodologies, using charge-particle energy-loss imaging techniques, only a few events are needed compared to many thousands required if attenuation measurements were to be employed. The energies of horizontal cosmic-ray muons are distributed largely between 0.1 and 1000 GeV with a mean energy of about 50 GeV. Radiation Transport Monte-Carlo methods (GEANT4) have been used to calculate the energy loss for a selection of industrial materials in the energy range of interest. The energy loss of the muons along a ray-sum are modelled and compared to attenuation losses along the ray-sum using energy resolving detectors in coincidence before and after the sample. The energy-loss spectra across different samples are measured, demonstrating that embedded materials can be identified with as few as 10 muons passing through the sample. It is proposed that the imaging modality can be extended into a full tomographic modality allowing material identification within each voxel.     

BUBBLE MEASUREMENTS IN A GAS-LIQUID JET

Measurements have been carried out in the developing and fully developed regions of a free, axisymmetric, isothermal, air-water, bubbly jet. Three experiments have been conducted at a fixed jet-exit Reynolds number and gas superficial velocity using three different bubble injector assemblies producing bubbles of moderately different average sizes and size distributions. The volume fraction of the bubbly jet flow examined in this study is low and the resulting dispersed flow is dilute. A one-component Phase-Doppler Velocimetry system has been employed to measure bubble size and velocity non-intrusively. Visual data collected simultaneously with the light-scattering measurements were analyzed with the aid of image processing and used to verify the trends portrayed by the light-scattering measurements and to determine average bubble size. Our measurements show that, even in the dilute flow examined here, differences in initial bubble-size and size distribution can influence the RMS velocity fluctuations of the bubbles, particularly in the jet development region. The average bubble velocities are less sensitive. Evidence that the development pattern of the jet near the exit is affected by the presence of the bubbles is also presented. Near the exit of the jet, bubbles are shown to be ejected laterally outside the jet due to the significant lift force caused by the high velocity gradient in the axisymmetric shear layer. The observed sensitivity of the bubble flow to size-related parameters and initial conditions in this dilute case, indicates that discrepancies in previous measurements of dispersed, bubbly flows could be attributed to different size characteristics and/or initial conditions.     

Improving the colour fastness of dyed nylon‐6 fabric by graft copolymerisation and curing of acrylic acid

The influence of grafting and grafting–curing of acrylic acid on the colour fastness of nylon‐6 fabric dyed with an acid dye of low wash fastness was investigated. The variables involved in grafting were initially optimised for pristine nylon‐6 fabric prior to grafting the same monomer onto the dyed fabrics. The highest graft yield achieved for the pristine and dyed nylon‐6 fabrics was 44 and 14% respectively. Grey scale testing and colorimetric analysis revealed that the highest colour fastness and the smallest drop in colour strength belonged to the dyed–grafted–cured nylon‐6 fabric. The colour components were measured, and the total colour difference of each sample after five washing cycles was computed. The specific colour difference showed that the implementation of either grafting or grafting–curing processes will alter the reference colour of the dyed fabric. The tensile strength of the grafted and grafted–cured fabrics was respectively 2.7 and 6.3% lower than that of dyed nylon‐6.     

High temperature mechanical behavior of porous ceria and ceria-based solid-oxide fuel cells

Multiple environment mechanical testing of solid-oxide fuel cells (SOFCs) and SOFC materials is critical to ensure appropriate compressive sealing in stack designs. Establishing the effects of temperature, environment, and porosity on the flexural strength of ceria-based SOFCs is a significant step toward practical deployment of the technology. This article presents research into these properties by use of a temperature and atmosphere controlled 3-point bend fixture capable of reaching Intermediate Temperature (IT)-SOFC operating conditions (650°C). Gadolinium-doped ceria (GDC) samples with varying porosity and pore geometry were tested and it was determined that more spherical porosity contributed to improved flexural strength as compared with higher aspect ratio porosity. A linear strengthening effect was also observed with increasing temperature from ambient to 650°C for GDC-based anode support layers and half-cell samples. Scanning electron microscopy was performed on fracture surfaces to identify fracture modes and to examine internal pore structures. Directionality of the applied stress with respect to the layered microstructure was found to have no measurable impact on mechanical properties in air, but orientation had a significant impact on strength of cells with reduced anodes. Additionally, with the support of thermogravimetric analysis, it was determined that after reduction, exposure to oxygen below 100°C does not influence mechanical properties of the cells.