Epoxy composite coating systems generally find their usage in applications such as, fluid handling systems to protect components from corrosive media. However, their use in demanding tribological ...applications such as, in sliding components of machines, are known to be limited. This is often attributed to their low load bearing capacity combined with poor thermal stability under severe
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regimes. Researchers have tried to enhance the tribological properties of the epoxy coatings using a combination of several types of micro/nano sized fillers to produce composite or hybrid composite coatings. Hence, this review paper aims to focus on the recent advances made in developing the epoxy coating systems. Special attention would be paid to the types and properties of nano-fillers that have been commonly used to develop these coatings, different dispersion techniques adopted and the effects that each of these fillers (and their combinations) have on the tribological properties of these coatings.
An attempt is made to cover the whole of the topic of biodegradable magnesium (Mg) alloys with a focus on the biocompatibility of the individual alloying elements, as well as shed light on the ...degradation characteristics, microstructure, and mechanical properties of most binary alloys. Some of the various work processes carried out by researchers to achieve the alloys and their surface modifications have been highlighted. Additionally, a brief look into the literature on magnesium composites as also been included towards the end, to provide a more complete picture of the topic. In most cases, the chronological order of events has not been particularly followed, and instead, this work is concentrated on compiling and presenting an update of the work carried out on the topic of biodegradable magnesium alloys from the recent literature available to us.
LASER induced breakdown spectroscopy (LIBS) has been used for the quantitative analysis of Cu–Ni alloy of known composition (75% Cu, 25% Ni) using the one line calibration free-LIBS (OLCF-LIBS), ...self-calibration-LIBS (SC-LIBS), calibration free LIBS (CF-LIBS), time of flight-mass spectroscopy (TOF-MS), energy dispersive X-ray spectroscopy (EDX) and X-ray fluorescence spectroscopy (XRF). For the LIBS-based studies, the plasma was generated by focusing the beam of a Q-switched Nd:YAG laser (532 nm, pulse energy about 200 mJ, 5 ns pulse duration) while the sample was placed in air at an atmospheric pressure. Plasma temperature about (9500 ± 300) K was calculated by the Boltzmann plot method using the neutral lines of Cu and Ni whereas the electron number density was calculated (2.0 ± 0.5) × 1016 cm−3 from the Stark broadening of an isolated Cu line as well as using the relative intensities of the neutral and singly ionized optically thin lines in the Saha–Boltzmann equation. The elemental compositions determined by different LIBS methods and standard techniques are; OLCF-LIBS (69% Cu and 31% Ni), SC-LIBS (72% Cu and 28% Ni), CF-LIBS (74% Cu and 26% Ni), TOF (74% Cu and 26% Ni), EDX (75% Cu and 24.5% Ni), XRF (73% Cu and 24.7% Ni), and LA-TOF (74% Cu and 26% Ni). It is demonstrated that the CF-LIBS method gives compositions comparable with that determined by LA-TOF, EDX, or XRF, which is also in agreement with the certified reported composition.
Desalination of seawater and brackish water is becoming an increasingly important means to address the scarcity of fresh water resources in the world. Decreasing the energy requirements and ...infrastructure costs of existing desalination technologies remains a challenge. By enabling the manipulation of matter and control of transport at nanometer length scales, the emergence of nanotechnology offers new opportunities to advance water desalination technologies. This review focuses on nanostructured materials that are directly involved in the separation of water from salt as opposed to mitigating issues such as fouling. We discuss separation mechanisms and novel transport phenomena in materials including zeolites, carbon nanotubes, and graphene with potential applications to reverse osmosis, capacitive deionization, and multi-stage flash, among others. Such nanostructured materials can potentially enable the development of next-generation desalination systems with increased efficiency and capacity.
Abstract
This paper presents comparative evaluation of an application of deep convolutional neural networks (dCNNs) to age invariant face recognition. To this end, we use four distinct dCNN models, ...the AlexNet, VGGNet, GoogLeNet and ResNet. We assess their performance to recognize face images across aging variations, firstly by fine-tuning the models and secondly using them as face feature extractor. We also suggest a novel synthesized aging augmentation technique suitable for age-invariant face recognition using dCNNs. The face recognition experiments are conducted on three challenging FG-NET, MORPH and LAG aging datasets, and results are benchmarked with a simple CNN. The comparative study allows us to answer (i) when and why transfer learning or feature extraction strategies are useful in age-invariant face recognition scenarios, (ii) the potential of aging synthesized augmentation to increase accuracy and (iii) the choice of appropriate feature normalization and distance metrics to be used with deeply learned features. The extensive experiments, and valuable insights presented in this study can be extended to the design of effective age-invariant face recognition algorithms.
Study of various binding materials like potassium bromide, poly(vinyl alcohol), starch, silver and aluminum has been carried out using laser-induced breakdown spectroscopy (LIBS). The role of matrix ...effects using these five binders on LIBS signal intensity was investigated for better performance of LIBS technique as a quantitative analytical tool. For comparative study of different binders, the signal intensity of different Mg lines at 518.3, 517.2, 383.8 and 279.5
nm wavelengths were recorded for pellets prepared with known concentrations of Mg in these binders. The influence of laser energy on ablated mass under different binding materials and its correlation with LIBS signal intensity has been explored. Optical scanning microscopy images of the ablated crater were studied to understand the laser ablation process. The study revealed that the binding material plays an important role in the generation of LIBS signal. The relative signal intensity measured for a standard Mg line (at 518.3
nm) were 735, 538, 387, 227 and 130 for potassium bromide, starch, poly(vinyl alcohol), silver and aluminum as binders, respectively. This indicates clearly that potassium bromide is better as a binder for LIBS studies of powder samples.
Due to large growth in leather and textile industries to cater for the needs of a growing world population, contamination of soil and water resources by chromium has become a great threat for humans ...and animals. In this work, Laser Induced Breakdown Spectroscopy (LIBS) was applied to monitor the remediation process of soil contaminated with Chromium metal. This study was conducted at a laboratory scale by setting up an experiment in a container holding soil contaminated with chromium. This setup represents actual field conditions where remediation process could be applied and monitored for the removal of toxic metals like Cr. For generation of LIBS spectrum, the plasma was produced by focusing a pulsed Nd: YAG laser at 1064
nm on the soil contaminated with chromium under remediation process. The evaluation of the potential and capabilities of LIBS as a rapid tool for remediation process of contaminated sites is discussed in detail. Optimal experimental conditions were evaluated for improving the sensitivity of our LIBS system for monitoring of remediation process through parametric dependence study. The minimum detection limit of our spectrometer for chromium in soil matrix was 2
mg
Kg
−1.
This article reviews the application of highly heat and pressure resistant polyimide material for the development of membranes/materials that exhibit unique super-wettability, the characteristics ...pivotal for the efficient separation of oil-water mixture and emulsion. The polymerization of imide monomer in polyimide brings about the required porosity in the material, which in turn renders the crucial surface roughness, which is instrumental for establishing the desired super-wettability on the polyimide based membrane materials, in addition to the mechanical and thermal robustness. The membrane as the oil-water filtering medium can be either oil passing or water passing depends on the individual wettability of the membrane surface for oil and water, which in turn depend on the respective solid-liquid interfacial energy and the hierarchical surface roughness. Superhydrophobic/superoleophobic wetting characteristic of the surface repels water and allows oil to pass through the membrane medium, and the major disadvantage of this kind of oil/water separation is the rapid oil fouling of the membrane pores and the consequent less efficiency for oil water separation. On the other hand, the membrane surface engineered to have the Superhydrophilic/underwater superoleophobic wetting characteristics can be water passing, and the easy fouling of the membrane surface can be minimized. In the case of polyimide materials, there are lot of scopes to engineer the physical properties like surface energy and surface roughness of the membrane surface in order to obtain the required wettability. There have been many works focused on the application of different variants of polyimide materials for developing membrane for oil water separation. In this review, we present an itemized review of various works on polyimide materials based oil/water separation in terms of chemical, physical, structural and surface characteristics of the material.
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•Innovative polyimide based membrane surfaces that exhibit unique super-wettability.•Special wetting/non-wetting surfaces for oil-water mixture and emulsion separations.•Novel review of these membranes/materials for high performance oil-water separation.•State-of-the-art advances of polyimide based super-wettable membranes are discussed.
The mobility, availability and persistence of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn) in contaminated lake sediment samples were evaluated by means of sequential extraction scheme, proposed by the ...Community Bureau of Reference protocol (BCR). The metal content in the extracts was measured by atomic absorption spectrometry. The precision and accuracy of the proposed procedure were evaluated by using a certified reference material BCR 701. The maximum recoveries for heavy metals (HMs) were observed for all three steps of BCR protocol at 32
h total shaking period instead of previously reported 51
h, with
p
>
0.05. The lixiviation tests (DIN 38414-S4) were used to evaluate the leaching of HMs from sediment samples and it was observed that levels of water extractable HMs were low as compared to those values obtained by acid-soluble fraction of the BCR protocol.
The present investigation is primarily aimed to investigate the impact of thiourea on characteristic properties of ammonium dihydrogen phosphate (NH4H2PO4, ADP) crystal to emphasize its utmost ...liability for designing nonlinear optical device applications. The most commercial slow solvent evaporation method has been opted to grow the undoped and thiourea doped ADP single crystals. The single crystal X-ray diffraction study has been employed to determine the structural parameters of undoped and thiourea doped ADP crystal. The elemental analysis has been performed to confirm the presence of thiourea in ADP crystal. The UV–visible studies have been carried out within 200–1100 nm to examine the constructive impact of thiourea on optical transparency and vital linear optical parameters (extinction coefficient, refractive index and reflectance) of ADP crystal. The Kurtz-Perry test has been employed to ascertain the enhancement in SHG efficiency of ADP crystal due to presence of thiourea. The third order nonlinear optical nature and properties such as nonlinear absorption (β), refraction (n2) and susceptibility (χ3) of T-ADP crystal has been examined at 632.8 nm by imposing the Z-scan studies. The color centered photoluminescence emission behavior of pure and thiourea doped ADP crystal has been investigated within 320–650 nm. Vickers microhardness study has been imposed to evaluate the role of thiourea in uplifting the hardness parameters of ADP crystal. The dielectric parameters (dielectric constant and dielectric loss) of undoped and thiourea doped ADP crystal has been comparatively investigated within the temperature range of 25–100 °C. The surface growth habitat of thiourea doped ADP crystal has been investigated by means of chemical etching technique.
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•Bulk single crystal growth of thiourea doped ADP (T-ADP) was achieved.•Thiourea significantly improved the linear optical properties of ADP.•The SHG efficiency of T-ADP = 1.28 (ADP).•TONLO properties n2, β and χ3 of T-ADP is of order 10−8 cm2/W, 10−2 cm/W and 10−2 esu.•T-ADP crystal has better dielectric and microhardness properties as compared to ADP.
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