Segmentation of images from scanning electron microscope, especially multiphase, poses a drawback in their microstructure quantification process. The labeling process must be automatized due to the time consumption and irreproducibility of the manual labeling procedure. Here we show a swarm intelligence-driven filtration methodology performed on raw solid oxide fuel cell anode’s material images to improve the segmentation methods’ performance. The methodology focused on two significant parts of the segmentation process, which are filtering and labeling. During the first one, the images underwent filtering by applying a series of filters, whose operation parameters were determined using Particle Swarm Optimization upon a dedicated cost function. Next, Seeded Region Growing, k-Means Clustering, Multithresholding, and Simple Linear Iterative Clustering Superpixel algorithms were utilized to label the filtered images’ regions into consecutive phases in the microstructure. The improvement w... [more]

Work was carried out to diagnose irregularities in the operation of a vacuum-tube solar collector. Experimental investigations of the collector were carried out at the solar collector field test stand in the Laboratory of Solar Collectors at the Koszalin University of Technology. The scope of the work included the following: research on thermal efficiency characteristics, research on the temperature distribution on the solar collector manifold, and research on the geometric structure of the heat pipe and filling with the working medium. Based on the diagnostic tests carried out, the occurrence of incorrect sedimentation in the condenser on the neck of the heat pipe (44%) and an incorrect amount of working medium (66%) were found. The results show that the functioning of the heat pipe significantly depends on its geometric structure and the amount of working medium. Any irregularity at the production stage contributes to a reduction in the thermal efficiency of the solar collector. The... [more]

Latent heat storage units for refrigeration processes are promising as alternatives to water/glycol-based storage due to their significantly higher energy densities, which would lead to more compact and potentially more cost-effective storages. In this study, important thermophysical properties of five phase change material (PCM) candidates are determined in the temperature range between −22 and −35 °C and their compatibility with relevant metals and polymers is investigated. The goal is to complement existing scattered information in literature and to apply a consistent testing methodology to all PCMs, to enable a more reliable comparison between them. More specifically, the enthalpy of fusion, melting point, density, compatibility with aluminum, copper, polyethylene (PE), polypropylene (PP), neoprene and butyl rubber, are experimentally determined for 1-heptanol, n-decane, propionic acid, NaCl/water mixtures, and Al(NO3)3/water mixtures. The results of the investigations reveal indiv... [more]

Li-ion capacitors (LICs) are designed to achieve high power and energy densities using a carbon-based material as a positive electrode coupled with a negative electrode often adopted from Li-ion batteries. However, such adoption cannot be direct and requires additional materials optimization. Furthermore, for the desired device’s performance, a proper design of the electrodes is necessary to balance the different charge storage mechanisms. The negative electrode with an intercalation or alloying active material must provide the high rate performance and long-term cycling ability necessary for LIC functionality—a primary challenge for the design of these energy-storage devices. In addition, the search for new active materials must also consider the need for environmentally friendly chemistry and the sustainable availability of key elements. With these factors in mind, this review evaluates advanced and emerging materials used as high-rate anodes in LICs from the perspective of their pra... [more]

Two-tank metal hydride pairs have gained tremendous interest in thermal energy storage systems for concentrating solar power plants or industrial waste heat recovery. Generally, the system’s performance depends on selecting and matching the metal hydride pairs and the thermal management adopted. In this study, the 2D mathematical modeling used to investigate the heat storage system’s performance under different thermal management techniques, including active and passive heat transfer techniques, is analyzed and discussed in detail. The change in the energy storage density, the specific power output, and the energy storage efficiency is studied under different heat transfer measures applied to the two tanks. The results showed that there is a trade-off between the energy storage density and the energy storage efficiency. The adoption of active heat transfer enhancement (convective heat transfer enhancement) leads to a high energy storage density of 670 MJ m−3 (close to the maximum theor... [more]

In this paper, we experimentally investigated two high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) stacks for their response to the presence of reformate impurities in an anode gas stream. The investigation was aimed at characterizing the effects of reformate impurities at the stack level, including in humidified conditions and identifying fault features for diagnosis purposes. Two HT-PEMFC stacks of 37 cells each with active areas of 165 cm2 were used with one stack containing a pre-doped membrane with a woven gas diffusion layer (GDL) and the other containing a post-doped membrane with non-woven GDL. Polarization curves and galvanostatic electrochemical impedance spectroscopy (EIS) were used for characterization. We found that both N2 dilution and impurities in the anode feed affected mainly the charge transfer losses, especially on the anode side. We also found that humidification alleviated the poisoning effects of the impurities in the stack with pre-doped membra... [more]

The Ni-containing catalysts based on ceria−zirconia doped with Ti and Ti+Nb were prepared by the solvothermal method in supercritical fluids. Ni deposition was carried out by incipient wetness impregnation and the one-pot technique. All materials were investigated by a complex of physicochemical methods (XRD, BET, TEM, H2-TPR). Samples catalytic properties were studied in methane dry reforming in the plug-flow reactor. Conversions of CH4 and CO2, H2/CO ratio, and CO and H2 yields were measured, and detailed kinetics analysis was carried out. The influence of Ni loading method and support modification on the catalytic behavior in the methane dry reforming process was studied. The preparation method of catalysts affects the textural characteristics. For one-pot samples, pore volume and surface area are lower than for impregnated samples. For catalysts on modified supports, strong metal−support interaction was shown to increase catalytic activity. A reduction pretreatment of samples was s... [more]

Hydrothermal carbonization (HTC) is considered as an efficient and constantly expanding eco-friendly methodology for thermochemical processing of high moisture waste biomass into solid biofuels and valuable carbonaceous materials. However, during HTC, a considerable amount of organics, initially present in the feedstock, are found in the process water (PW). PW recirculation is attracting an increasing interest in the hydrothermal process field as it offers the potential to increase the carbon recovery yield while increasing hydrochar energy density. PW recirculation can be considered as a viable method for the valorization and reuse of the HTC aqueous phase, both by reducing the amount of additional water used for the process and maximizing energy recovery from the HTC liquid residual fraction. In this work, the effects of PW recirculation, for different starting waste biomasses, on the properties of hydrochars and liquid phase products are reviewed. The mechanism of production and evo... [more]

Solute tracer tests are an established method for the characterization of flow and transport processes in fractured rock. Such tests are often monitored with borehole sensors which offer high temporal sampling and signal to noise ratio, but only limited spatial deployment possibilities. Ground penetrating radar (GPR) is sensitive to electromagnetic properties, and can thus be used to monitor the transport behavior of electrically conductive tracers. Since GPR waves can sample large volumes that are practically inaccessible by traditional borehole sensors, they are expected to increase the spatial resolution of tracer experiments. In this manuscript, we describe two approaches to infer quantitative hydrological data from time-lapse borehole reflection GPR experiments with saline tracers in fractured rock. An important prerequisite of our method includes the generation of GPR data difference images. We show how the calculation of difference radar breakthrough curves (DRBTC) allows to ret... [more]

Retro-reflectivity is a promising surface capability, which has attracted the interest of researchers for building applications in order to counteract Urban Heat Island (UHI) effects. This work aims at studying the impact of the substrate material on the optic performance of retro-reflective (RR) coatings. Three types of substrate materials were investigated: smooth pine wood panels, rough plywood panels, and smooth acetate sheets. The RR coating samples were made by firstly adding a high reflective white paint onto the substrate material and a homogeneous RR glass beads layer on the top. As a reference case, also diffusive samples, without RR beads, were developed. Samples have been tested through a spectrophotometric and an angular reflectivity analysis. Results show that, despite a lower global reflectance of the RR samples with respect to the diffusive ones, the glass beads coating provides a good retro-reflective capability to all the diffusive samples. Additionally, the roughest... [more]

In this work, temperature regulation and electrical output of a concentrated photovoltaic system coupled with a phase change material (CPVPCM) system is investigated and compared with a single sun crystalline photovoltaic (PV) system. A fully coupled thermal-optical-electrical model has been developed in-house to conduct the simulation studies for actual weather conditions of Doha (Qatar) and selected phase change materials (PCMs). The selected PCMs are lauric acid, RT47, S-series salt, STL47, ClimSelTM C48, RT54, RT60, RT62, and RT64. An optical concentration ratio of 20× is considered on a 15 mm wide crystalline silicon cell. The temperature evolution, thermal energy storage and electrical output of the CPVPCM system are obtained for 48-hour simulations with representative weather conditions for each month of a typical meteorological year (TMY). Results and overall thermal and electrical efficiency are compared for each PCM. In brief, the CPVPCM system with S-series salt performs bet... [more]

The results of free convection heat transfer investigation from a horizontal, uniformly heated tube immersed in a nanofluid are presented. Experiments were performed with five base fluids, i.e., ethylene glycol (EG), distilled water (W) and the mixtures of EG and water with the ratios of 60/40, 50/50, 40/60 by volume, so the Rayleigh (Ra) number range was 3 × 104 ≤ Ra ≤ 1.3 × 106 and the Prandtl (Pr) number varied from 4.4 to 176. Alumina (Al2O3) nanoparticles were tested at the mass concentrations of 0.01, 0.1 and 1%. Enhancement as well as deterioration of heat transfer performance compared to the base fluids were detected depending on the composition of the nanofluid. Based on the experimental results obtained, a correlation equation that describes the dependence of the average Nusselt (Nu) number on the Ra number, Pr number and concentration of nanoparticles is proposed.

Carbon nanotubes (CNTs) are being increasingly studied as electrode materials for supercapacitors (SCs) due to their high electronic conductivity and chemical and mechanical stability. However, their energy density and specific capacitance have not reached the commercial stage due to their electrostatic charge storage system via a non-faradic mechanism. Moreover, magnetite (Fe3O4) exhibits higher specific capacitance originating from its pseudocapacitive behaviour, while it has irreversible volume expansion during cycling. Therefore, a very interesting and facile strategy to arrive at better performance and stability is to integrate CNTs and Fe3O4. In this study, we demonstrate the microwave-solvothermal process for the synthesis of Fe3O4 nanoparticles uniformly grown on a CNT composite as an electrode for SCs. The synthesized Fe3O4/CNT composite delivers a reversible capacitance of 187.1 F/g at 1 A/g, superior rate capability by maintaining 61.6% of 10 A/g (vs. 1 A/g), and cycling sta... [more]

This experimental study was carried out based on the nanotechnology approach to enhance the efficacy of engine oil. Atomic and surface structures of graphene oxide (GO) nanoparticles were investigated by using a field emission scanning electron microscope and X-ray diffraction. The nano lubricant was produced by using a two-step method. The stability of nano lubricant was analyzed through dynamic light scattering. Various properties such as thermal conductivity, dynamic viscosity, flash point, cloud point and freezing point were investigated and the results were compared with the base oil (Oil- SAE-50). The results show that the thermal conductivity of nano lubricant was improved compared to the base fluid. This increase was correlated with progressing temperature. The dynamic viscosity was increased by variations in the volume fraction and reached its highest value of 36% compared to the base oil. The cloud point and freezing point are critical factors for oils, especially in cold sea... [more]

The analysis of porosity and pore structure of shale rocks has received special attention in the last decades as unconventional reservoir hydrocarbons have become a larger parcel of the oil and gas market. A variety of techniques are available to provide a satisfactory description of these porous media. Some techniques are based on saturating the porous rock with a fluid to probe the pore structure. In this sense, gases have played an important role in porosity and pore structure characterization, particularly for the analysis of pore size and shapes and storage or intake capacity. In this review, we discuss the use of various gases, with emphasis on N2 and CO2, for characterization of shale pore architecture. We describe the state of the art on the related inversion methods for processing the corresponding isotherms and the procedure to obtain surface area and pore-size distribution. The state of the art is based on the collation of publications in the last 10 years. Limitations of th... [more]

Nanomaterials with collective optical and magnetic properties are called smart or functional materials and have promising applications in many fields of science and technology. Undoped and Co-doped ZnAl2O4 were prepared using a co-precipitation-assisted hydrothermal method. A systematic investigation was carried out to understand the effects of the Co concentration on the crystalline phase, morphology, and optical and magnetic properties of Co-doped ZnAl2O4. X-ray diffraction confirmed the cubic spinel structure with the Fd3m space group, and there was no impurity phase. X-ray photoelectron spectroscopy of Co-doped ZnAl2O4 confirmed the existence of Zn, Al and O, and the Co in the optimized sample of ZAO-Co-3 confirmed the oxidation state of cobalt as Co2+. Transmission electron microscopy of pure and Co-doped ZnAl2O4 revealed micro-hexagons and nanosheets, respectively. The optical absorption results showed that the bandgap of ZnAl2O4 decreased with increasing Co concentration. The hy... [more]

Research on using phase change material (PCM) suspension to improve the heat transfer and energy storage capabilities of thermal systems is booming; however, there are limited studies on the application of PCM suspension in transient natural convection. In this paper, the implicit finite difference method was used to numerically investigate the transient and steady-state natural convection heat transfer in a square enclosure containing a PCM suspension. The following parameters were included in the simulation: aspect ratio of the physical model = 1, ratio of the buoyancies caused by temperature and concentration gradients = 1, Raleigh number (RaT) = 103−105, Stefan number (Ste) = 0.005−0.1, subcooling factor (Sb) = 0−1.0, and initial mass fraction (or concentration) of PCM particles (ci) = 0−0.1. The results showed that the use of a PCM suspension can effectively enhance heat transfer by natural convection. For example, when RaT = 103, Ste = 0.01, ci = 0.1, and Sb = 1, the steady-state... [more]

The uniquely soft and fragile nature of tectonic coal makes it difficult to obtain core samples suitable for laboratory experimentation. Preparation of reconstituted tectonic coal (RTC) samples generally adopts the secondary forming method. Reliable coal samples are needed to obtain credible permeability and mechanical parameters that can guide Coalbed Methane (CBM) extraction and improve mining safety. In this study, the compaction mechanism of coal particles is analyzed based on the Kawakita model, and optimal sample preparation conditions are systemically investigated, particularly particle size and particle size distribution, forming pressure, and moisture content. The density and P-wave velocity of coal samples were used to test whether the RTC samples were realistic. Finally, the mechanical properties and deformation characteristics of the RTC samples were determined. The results indicate that RTC samples prepared for laboratory testing of mechanical properties require (1) the or... [more]

This study investigated the self-sensing mechanism in the electromagnetic vibration-based energy harvester (EV-EH) prototype specially engineered for a commercial magnetorheological (MR) damper. The objective of the work is to demonstrate that the EV-EH unit with a specific self-powered feature can also be employed as a relative velocity sensor in the system. To do this, the self-sensing action of the unit was experimentally studied over the assumed range of working conditions. The analysis of the test results and the determined self-sensing function indicated that the EV-EH has a highly accurate monitoring capability. The EV-EH self-sensing and self-powered features confirm the potentials and applicability of the unit for MR damper control in a vibration reduction system with energy regeneration.

The development of a selective and efficient catalyst for CO2 electroreduction is a great challenge in CO2 storage and conversion research. Silver metal is an attractive alternative due to its enhanced catalytic performance of CO2 electroreduction to CO. Here, we prepared Ag nanowires anchored on carbon support as an excellent electrocatalyst with remarkably high selectivity for the CO2 reduction to CO. The CO Faradic efficiency was approximately 100%. The enhanced catalytic performances may be ascribed to dense active sites exposed on the Ag nanowires’ high specific surface area, by the uniform dispersion of Ag nanowires on the carbon support. Our research demonstrates that Ag nanowires supported on carbon have potential as promising catalysts in CO2 electroreduction.

Due to the excellent impact resistant performance of steel-plate concrete (SC) structure compared with the conventional reinforced concrete (RC) structure, SC structure is preferred to be used in the design of external walls of nuclear island buildings for new nuclear power plants (NPPs). This study aims at evaluating the effect of material and geometric parameters of SC containment on its impact resistant performance, thus the numerical simulation and sensitivity analysis of SC containment subjected to malicious large commercial aircraft attack are conducted based on the force time-history analysis method. The results show that: (1) the impact resistant performance of full SC containment is better than that of half SC containment; (2) for relatively thin full SC containment, the impact response and concrete damage can be significantly reduced by the enhancing of concrete strength grade or the increasing of steel plate thickness; (3) for the thicker full SC containment, concrete streng... [more]

Empirical models continue to play a significant role in the design process of multiphase chemical reactors, particularly riser reactors in circulating fluidized bed (CFB) processes. It is imperative that accurate, industrial relevant correlations are developed to aid these design efforts. Using poor correlations could result in startup issues and significant redesign work. In this work, a new correlation is proposed to predict the saturation carrying capacity of Geldart Group A particles. This new correlation improves upon the currently available correlations for these materials and covers a broad range of Geldart Group A particles (particle diameters from 52 to 70 µm, and Archimedes numbers ranging from 5 to 20), superficial gas velocities (1 to 4 m/s), and riser diameters (0.066 to 0.3048 m). The new correlation has an Absolute Average Percent Deviation of only 17.6%, making it the most accurate correlation for Geldart Group A particles in the current literature.

The paper presents research on magnetic field exciters dedicated to testing magnetocaloric materials (MCMs) as well as used in the design process of magnetic refrigeration systems. An important element of the proposed test stand is the system of magnetic field excitation. It should provide a homogeneous magnetic field with a controllable value of its intensity in the MCM testing region. Several concepts of a magnetic circuit when designing the field exciters have been proposed and evaluated. In the MCM testing region of the proposed exciters, the magnetic field is controlled by changing the structure of the magnetic circuit. A precise 3D field model of electromagnetic phenomena has been developed in the professional finite element method (FEM) package and used to design and analyze the exciters. The obtained results of the calculations of the magnetic field distribution in the working area were compared with the results of the measurements carried out on the exciter prototype. The conc... [more]

With wind turbines increasing in size, installed at greater distances from the mainland, and greater depths, submarine cables are facing new challenges. Materials and technologies used so far for the production of submarine cables with lead, aluminium, or copper sheaths make them unsuitable or even obsolete for modern solutions such as floating wind farms. The article discusses types of submarine cables, their construction, working conditions, and operational factors, with emphasis placed on the role of the radial water barrier. The focus has been placed on dry and semi-dry designs. The article is also devoted to a discussion regarding directions of further development, possible materials, and constructions that may appear in the future. Current research and results regarding the use of multi-layer coatings with the use of thermoplastic block copolymers for the layer with high moisture absorption are also presented.

In this paper, the applications of thermoplastic, thermoset polymers, and a brief description of the functions of each subsystem are reviewed. The synthetic route and characteristics of polymeric materials are presented. The mechanical properties of polymers such as impact behavior, tensile test, bending test, and thermal properties like mold stress-relief distortion, generic thermal indices, relative thermal capability, and relative thermal index are mentioned. Furthermore, this paper covers the electrical behavior of polymers, mainly their dielectric strength. Different techniques for evaluating polymers’ suitability applied for electrical insulation are covered, such as partial discharge and high current arc resistance to ignition. The polymeric materials and processes used for manufacturing cables at different voltage ranges are described, and their applications to high voltage DC systems (HVDC) are discussed. The evolution and limitations of polymeric materials for electrical appl... [more]