Applied Sciences — Open Access Journal

As a novel non-destructive testing technique, capacitive imaging (CI) has been used to detect defects within the insulation layer and metal surface of an insulated metallic structure, that is, pipe or vessel. Due to the non-linearity of the probing field, the defects at different depths in the insulation layer are difficult to compare accurately using the conventional CI sensor with a single pair of electrodes. In addition, the conventional CI sensor cannot provide adequate information to discriminate the defects in the insulation layer and metal surface. In order to solve the above-mentioned problems, the multi-electrode sensor is introduced. The multi-electrode sensor uses multiple quasi-static fringing electric fields generated by an array of coplanar electrodes to obtain extra information about the defects in the specimen. In this work, the feasibility of multiple quasi-static electric fields detecting the defects was demonstrated and the Measurement Sensitivity Distributions (MSDs) of the multi-electrode sensor detecting the defects were acquired using the FEM models. The simulation and experimental results show that the Dynamic Change Rates (DCRs) of the measured values obtained at the center of the defects in the insulator layer and metal surface present different variation patterns, which can be used to discriminate these two different kinds of defects. The reasons for the different variation patterns of DCRs were explained by the changing trends of MSDs with increased electrode separation. In addition, it was demonstrated that the different depths of the defects in the insulator layer can be compared accurately by comprehensive analysis of the detection results from all the electrode pairs. Full article

We explored the occurrence and distribution of nonylphenol (NP) in 13 Taiwanese source waters. From all the surveyed waters, NP was detected at a high concentration, which could be attributed to contamination by wastewater discharges. In this study, we applied modified multi-walled carbon nanotubes (MWCNTs) for removing NP from aqueous solution. The impact of a few experimental factors, i.e., pH, contact time, MWCNTs dose, and temperature on the NP removal efficiency of modified MWCNTs was studied. The maximum adsorption capacity of the MWCNTs was observed to be 1040 mg NP/g when the initial NP concentration was 2.5 mg/L, and the solution pH was 4. The adsorption process followed the Elovich kinetics and the Elovich isotherm, indicating it is multilayer adsorption. The thermodynamic analysis demonstrated the NP adsorption by MWCNTs was thermodynamically satisfactory and, for the most part, endothermic as in the case of phenol adsorption. The result of the current study demonstrated the significance of free binding sites and the pore size of MWCNTs in the NP adsorption. This paper will help to better comprehend the adsorption behavior and mechanism of alkyl phenolic compounds onto MWCNTs. Full article

Object tracking is a computer vision task deemed necessary for high-level intelligent decision-making algorithms. Researchers have merged different object tracking techniques and discovered a new class of hybrid algorithms that is based on embedding a meanshift (MS) optimization procedure into the particle filter (PF) (MSPF) to replace its inaccurate and expensive particle validation processes. The algorithm employs a combination of predetermined features, implicitly assuming that the background will not change. However, the assumption of fully specifying the background of the object may not often hold, especially in an uncontrolled environment. The first innovation of this research paper is the development of a dynamically adaptive multi-feature framework for MSPF (AMF-MSPF) in which features are ranked by a ranking module and the top features are selected on-the-fly. As a consequence, it improves local discrimination of the object from its immediate surroundings. It is also highly desirable to reduce the already complex framework of the MSPF to save resources to implement a feature ranking module. Thus, the second innovation of this research paper introduces a novel technique for the MS optimization method, which reduces its traditional complexity by an order of magnitude. The proposed AMF-MSPF framework is tested on different video datasets that exhibit challenging constraints. Experimental results have shown robustness, tracking accuracy and computational efficiency against these constraints. Comparison with existing methods has shown significant improvements in term of root mean square error (RMSE), false alarm rate (FAR), and F-SCORE. Full article

In order to reduce the amount of abandoned clean energy, the complementary characterization of wind power plants (WPPs), photovoltaic power plants (PVs), hydropower stations (HSs), and thermal power plants (TPPs) combined with energy storage devices (ESDs) is considered, and they are integrated into a multi-energy complementary system (MECS). Firstly, a scenario-generating technique is proposed for uncertainty factors using the Wasserstein method and the improved K-medoids theory. Then, a multi-objective model and solution algorithm are constructed under the objectives of attaining the maximum operation revenue, the minimum abandoned energy cost, and the minimum output fluctuations. Meanwhile, the influence of different ESD operation modes on MECS operation is discussed, specifically, the longest life cycle (LLC) and the optimum economic efficiency (OEE). Thirdly, in order to solve the multi-objective model, a solution algorithm is proposed by using the rough set method to convert the multi-objective model into a single objective model based on the payoff table. Moreover, the complementary features of the MECS are evaluated in terms of the load tracking degree, HS secondary peaking capacity, and units of coal consumption. Finally, the improved IEEE 14-bus system is chosen for the simulation analysis. The results show that (1) the proposed uncertainty simulation method can efficiently generate the most representative scenarios; (2) MECSs can utilize complementary power sources, the OEE mode can better optimize MECS scheduling, and the LLC mode can ensure the ESDs’ life cycles; (3) the scheduling scheme of MECS operation reach the optimal level when the capacity ratio of ESD:WPP–PV iso [0.62, 0.77] in the OEE mode and [1, 1.08] in the LLC mode on a typical summer day, and the ratio is [0.92, 1] in the OEE mode and [1.23, 1.31] in the LLC mode on a typical winter day. Therefore, the proposed model provides effective decision-making support for designing the optimal plan for MECS operation. Full article

Accurate meteorological forecasting has great importance in different fields. This works introduces a system to obtain precise predictions, which uses regression functions, and collected data using the meteorological stations from the Gran Canaria and South Tenerife airports. The dataset offers information about different phenomena as temperature, wind speed, solar radiation, pressure, moisture, cloudiness, rainfall and meteors. A preprocessing stage has been applied before prediction stage to adapt the collected data. A support vector machine, regression tree, and fit linear model are applied as regression functions. Results has been measured by the mean square error. These results reached an accuracy of 0.07 °C for temperature, 0.56 km/h for wind speed, 7.45 tenths of kJ/m² for solar radiation and 0.11 mm for precipitation. It shows the robustness of the multiparameter meteorological forecast approach. Full article

In this paper, we propose a multichannel active noise control (ANC) system with an optimal reference microphone selector based on the time difference of arrival (TDOA). A multichannel feedforward ANC system using upstream reference signals can reduce various noises such as broadband noise by arranging reference microphones close to noise sources. However, the noise reduction performance of an ANC system degrades when the noise environment changes, such as the arrival direction. This is because some reference microphones do not satisfy the causality constraint that the unwanted noise propagates to the control point faster than the anti-noise used to cancel the unwanted noise. To solve this problem, we propose a multichannel ANC system with an optimal reference microphone selector. This selector chooses the reference microphones that satisfy the causality constraint based on the TDOA. Some experimental results demonstrate that the proposed system can choose the optimal reference microphones and effectively reduce unwanted acoustic noise. Full article

In line with global efforts at encouraging paradigm transitions from waste disposal to resource recovery, the anaerobic co-digestion of substrates of wet hydrolyzed meat processing dissolved air flotation sludge and meat processing stock yard waste was investigated in the present study. It was demonstrated that the co-digestion of these substrates leads to the introduction of co-digestion synergizing effects. This study assessed biomethane potentials of the co-digestion of different substrate mixtures, with the preferred substrate mixture composed of stockyard waste and wet hydrolyzed meat processing dissolved air flotation sludge, present in a 4:1 ratio on a volatile solid mass basis. This co-digestion substrate mix ratio presented an experimentally determined cumulative biomethane potential of 264.13 mL/gVS_added (volatile solid). The experimentally determined cumulative biomethane potential was greater than the predicted maximum cumulative biomethane potential of 148.4 mL/gVS_added, anticipated from a similar substrate mixture if synergizing effects were non-existent. The viability of integrating a downstream hydrothermal liquefaction processing of the digestate residue from the co-digestion process, for enhanced resource recovery, was also initially assessed. Assessments were undertaken via the theoretical based estimation of the yields of useful products of biocrude and biochar obtainable from the hydrothermal liquefaction processing of the digestate residue. The environmental sustainability of the proposed integrated system of anaerobic digestion and hydrothermal liquefaction technologies was also initially assessed. The opportunity for secondary resource recovery from the digestate, via the employment of the hydrothermal liquefaction process and the dependence of the environmental sustainability of the integrated system on the moisture content of the digestate, were established. It is anticipated that the results of this study will constitute an invaluable basis for the future large-scale implementation of the proposed integrated system for enhanced value extraction from organic waste streams. Full article

We present a type of eddy-current testing (ECT) method based on measuring the reaction of the Lorentz force by using a small permanent magnet (PM) as the probe. The means of measuring impedance is superseded by measuring force. By analyzing the variations in different components of the reaction of Lorentz force, the defects characteristics within the measured conductor can be revealed. The results indicate that the vector-based eddy-current testing method obtains good quantitative results and precisely evaluates the lift-off effect during measurement along two orthogonal directions. Numerical simulations are performed to provide supports for the experimental results. The method described in this paper may have great potential for use in industrial nondestructive testing applications. Full article

Establishing fast and reversible photon multiple scattering algorithms remains a modeling challenge for optical diagnostics and noise reduction purposes, especially when the scattering happens within the intermediate scattering regime. Previous work has proposed and verified a Markov chain approach for modeling photon multiple scattering phenomena through turbid slabs. The fidelity of the Markov chain method has been verified through detailed comparison with Monte Carlo models. However, further improvement to the Markov chain method is still required to improve its performance in studying multiple scattering. The present research discussed the efficacy of non-uniform discretization schemes and analyzed errors induced by different schemes. The current work also proposed an iterative approach as an alternative to directly carrying out matrix inversion manipulations, which would significantly reduce the computational costs. The benefits of utilizing non-uniform discretization schemes and the iterative approach were confirmed and verified by comparing the results to a Monte Carlo simulation. Full article

In the development of powered exoskeletons for paraplegics due to complete spinal cord injury, a convenient and reliable user-interface (UI) is one of the mandatory requirements. In most of such robots, a user (i.e., the complete paraplegic wearing a powered exoskeleton) may not be able to avoid using crutches for safety reasons. As both the sensory and motor functions of the paralyzed legs are impaired, the users should frequently check the feet positions to ensure the proper ground contact. Therefore, the UI of powered exoskeletons should be designed such that it is easy to be controlled while using crutches and to monitor the operation state without any obstruction of sight. In this paper, a UI system of the WalkON Suit, a powered exoskeleton for complete paraplegics, is introduced. The proposed UI system consists of see-through display (STD) glasses and a display and tact switches installed on a crutch for the user to control motion modes and the walking speed. Moreover, the user can monitor the operation state using the STD glasses, which enables the head to be positioned up. The proposed UI system is verified by experimental results in this paper. The proposed UI system was applied to the WalkON Suit for the torch relay of the 2018 Pyeongchang Paralympics. Full article

Organic inorganic hybrid perovskites have potential applications in solar cells, electroluminescent devices and radiation detection because of their unique optoelectronic properties. In this paper, the perovskites (C₆H₅CH₂NH₃)₂PbBr₄ and (C₆H₅CH₂NH₃)₂PbI₄ were synthesized by solvent evaporation. The crystal structure, morphology, absorption spectrum, laser power dependence of the photoluminescence (PL) intensity and lifetime were studied. The results showed that the perovskites (C₆H₅CH₂NH₃)₂PbBr₄ and (C₆H₅CH₂NH₃)₂PbI₄ display a layered stacking structure of organic and inorganic components. The absorption peaks are located at 392 nm (3.16 eV) and 516 nm (2.40 eV), respectively. It was observed that the PL intensity and photoluminescence quantum yield (PLQY) increases with increasing laser power, and that the PL lifetime decreases with increasing laser power, which is mainly due to the non-geminate recombination. Full article

In this study, functional coating film was fabricated on glass for photovoltaic (PV) modules to improve the anti-pollution characteristics of PV modules. The functional coating film applied to a glass substrate through the spray coating method was annealed at 300 °C for 10 min in H₂, N₂, Ar, O₂, and vacuum ambient. The contact angle of the coated surface was measured and it was confirmed that the anti-pollution characteristics were improved as the contact angle decreased. The light transmittance was measured and it exhibited the most excellent characteristics in vacuum. The hardness and adhesion were measured as the mechanical characteristics and they were all excellent regardless of the annealing ambient. Based on the analyzed characteristics, the process conditions of functional coating films were optimized to improve the anti-pollution and mechanical characteristics. If the coating process optimized in this study is applied to PV modules based on these results, improvement in the anti-pollution characteristics can be expected. Full article

Face alignment is the key component for applications such as face and expression recognition, face based AR (Augmented Reality), etc. Among all the algorithms, cascaded-regression based methods have become popular in recent years for their low computational costs and satisfactory performances in uncontrolled environments. However, the size of the trained model is large for cascaded-regression based methods, which makes it difficult to be applied in resource restricted scenarios such as applications on mobile phones. In this paper, a data compression method for the trained model of supervised descent method (SDM) is proposed. Firstly, according to the distribution of the model data estimated with the non-parametric method, a K-means based data quantization algorithm with probability density-aware initialization was proposed to efficiently quantize the model data. Then, a tightly-coupled SDM training algorithm was proposed so that the training process reduced the errors caused by data quantization. Quantitative experimental results proved that our proposed method compressed the trained model to less than 19% of its original size with very similar feature localization performance. The proposed method opens the gates to efficient mobile face alignment applications based on SDM. Full article

In this paper, an orthogonal type two-axis Lloyd’s mirror interference lithography technique was employed to fabricate two-dimensional planar scale gratings for surface encoder application. The two-axis Lloyd’s mirror interferometer is composed of a substrate and two reflective mirrors (X- and Y-mirrors), which are placed edge by edge perpendicularly. An expanded and collimated beam was divided into three beams by this interferometer, a direct beam and two reflected beams, projected onto the substrate, X- and Y-mirrors, respectively. The unexpected beam sections having twice reflected off the mirrors were blocked by a filter. The remaining two reflected beams interfered with the direct beam on the substrate, generating perpendicularly cross patterns thus forming two-dimensional scale gratings. However, the two reflected beams undesirably interfere with each other and generate a grating pattern along 45-degree direction against the two orthogonal direction, which influence the pattern uniformity. Though an undesired grating pattern can be eliminated by polarization modulation with introduction of waveplates, spatial configuration of waveplates inevitably downsized the eventual grating, which is a key parameter for grating interferometry application. For solving this problem, theoretical and experimental study was carefully carried out to evaluate the fabrication quality with and without polarization modulation. Two-dimensional scale gratings with a 1 μm period in X- and Y-directions were achieved by using the constructed experiment system with a 442 nm He-Cd laser source. Atomic force microscopy (AFM) images and the result of diffraction performances demonstrated that the orthogonal type two-axis Lloyd’s mirror interferometer can stand a small order undesired interference, that is, a degree of orthogonality between two reflected beams, denoted by γ, no larger than a nominal value of 0.1. Full article

Underground hydrogen storage is a potential way to balance seasonal fluctuations in energy production from renewable energies. The risks of hydrogen storage in depleted gas fields include the conversion of hydrogen to CH_4(g) and H₂S_(g) due to microbial activity, gas–water–rock interactions in the reservoir and cap rock, which are connected with porosity changes, and the loss of aqueous hydrogen by diffusion through the cap rock brine. These risks lead to loss of hydrogen and thus to a loss of energy. A hydrogeochemical modeling approach is developed to analyze these risks and to understand the basic hydrogeochemical mechanisms of hydrogen storage over storage times at the reservoir scale. The one-dimensional diffusive mass transport model is based on equilibrium reactions for gas–water–rock interactions and kinetic reactions for sulfate reduction and methanogenesis. The modeling code is PHREEQC (pH-REdox-EQuilibrium written in the C programming language). The parameters that influence the hydrogen loss are identified. Crucial parameters are the amount of available electron acceptors, the storage time, and the kinetic rate constants. Hydrogen storage causes a slight decrease in porosity of the reservoir rock. Loss of aqueous hydrogen by diffusion is minimal. A wide range of conditions for optimized hydrogen storage in depleted gas fields is identified. Full article

The mechanical behavior of the uranyl carbonate mineral, rutherfordine, UO₂CO₃, was studied by means of theoretical solid-state methods based in Density Functional Theory using plane waves and pseudopotentials. The results of the computations reported in this work show that this mineral exhibits the important negative Poisson ratio (NPR) phenomenon. In order to show that this feature is not an artifact associated to the theoretical treatment employed, additional calculations were carried out using very large calculation parameters. These calculations improved the mechanical description of this mineral and confirmed its auxeticity, i.e., it shows NPR values. Rutherfordine is a highly anisotropic material showing a maximum value of the NPR of the order of −0.3 ± 0.1 for applied stresses directed along the X axis, the transverse direction being the Y axis perpendicular to the structural sheets in rutherfordine structure. The underlying reason for this observation is that under the effect of applied positive pressures, the interlayer space between the sheets of rutherfordine vary in the opposite way to the expected behavior; that is, it decreases instead of increasing. Full article

Electrochemical deoxygenation of seawater has advantages over available chemical and physical methods. For seawater deoxygenation, acidic, neutral, or alkaline anolytes can be used. The effects of acidic, alkaline, and neutral buffered and non-buffered anolytes were studied in two compartment deoxygenation cells. The pH, conductivity, H₂O₂ production, and current were measured throughout the experiments. The optimum applied potentials for oxygen reduction were between 1.9 V–2.2 V, giving water as product; reducing the applied potential also resulted in the formation of H₂O₂. Analysis after the experiments using a scanning electron microscope with electron-dispersive X-ray spectroscopy showed that both the silver mesh and the cation exchange membrane remained stable during the experiments. The use of alkaline anolytes resulted in the maximum oxygen removal with minimal side reactions in the cell. Full article

Centralized/Cloud Radio Access Networks (C-RAN) are deployed in converged fixed-mobile networks to exploit the flexibility coming from joint application of Network Function Virtualization (NFV) and Software Defined Networking (SDN). In this context, optical links connecting C-RAN nodes, possibly based on the Ethernet standards, may carry traffic with different requirements in terms of latency and throughput. This paper considers the problem of traffic aggregation on C-RAN optical Ethernet links with latency control for fronthaul traffic and throughput capability for backhaul traffic. Integrated hybrid network technique is applied to show how time transparency can be enforced for Ethernet encapsulated Common Public Radio Interface (CPRI) traffic while allowing statistical multiplexing of backhaul traffic. Simulation results show the effectiveness of segmentation of backhaul traffic to allow exploitation of the available bandwidth even with high capacity CPRI options. Full article

The Smart Grid (SG) is nowadays an essential part of modern society, providing two-way energy flow and smart services between providers and customers. The main drawback is the SG complexity, with an SG composed of multiple layers, with devices and components that have to communicate, integrate, and cooperate as a unified system. Such complexity brings challenges for ensuring proper reliability, resilience, availability, integration, and security of the overall infrastructure. In this paper, we introduce a new smart grid testing management platform (herein called SGTMP) for executing real-time hardware-in-the-loop SG tests and experiments that can simplify the testing process in the context of interconnected SG devices. We discuss the context of usage, the system architecture, the interactive web-based interface, the provided API, and the integration with co-simulations frameworks to provide virtualized environments for testing. Furthermore, we present one main scenario about the stress-testing of SG devices that can showcase the applicability of the platform. Full article