Eng, Volume 3, Issue 1 (March 2022) – 14 articles

Planning and developing resilient socio-technical and natural systems to cope with and respond to unprecedented changes has been one of the top goals of government bodies, researchers, and practitioners worldwide. This study aims to review how resilience is defined and evaluated in water resources and infrastructure systems (hereafter water systems) and propose a framework to analyze and incorporate resilience in the system. Two questions guide the review: How is resilience defined in water systems compared to other disciplines? What are commonly used resilience measures and methods applicable to water systems? Based on the review, a resilience analysis framework has been proposed. The framework uses a system of systems approach and applies hierarchical holographic modeling to address the complexity of interdependent systems. The resilience of the systems was analyzed using three questions: resilience of what, resilience to what, and resilience for whom. Two resilience measures selected for the analysis are robustness and rapidity. The framework also includes methods for uncertainty analysis, options for resilience strategies, and multi-criteria decision analysis methods to select optimal resilience options. The review is not exhaustive due to the broader topic but aims to present necessary background information to support the proposed framework. Full article

Metal phosphates represent an important group of materials with established industrial applications that are still attracting special scientific interest, owing to their outstanding physical and chemical properties. In this review, we account on the different synthetic routes and applications of zirconium and titanium phosphates, with a special focus on their application in the medicinal field. While zirconium phosphate has been extensively studied and explored with several reported industrial and medicinal applications, especially for drug delivery applications, titanium phosphates have not yet attracted the deserved attention regarding their established applications. However, titanium phosphates have been the focus of several structural studies with their different polymorphic forms, varied chemical structures, and morphologies. These variations introduce titanium phosphates as a strong candidate for technological and, particularly, biomedical applications. Full article

Folded monopole structures have been used for many applications, including low-frequency electromagnetic wave transmission and reception. However, the literature on these antenna types is quite limited. Folded monopole antennas are mathematically complex compared to conventional monopole or dipole antennas since every fold introduces a new set of design parameters. This work studied the far-field radiation characteristics of multi-folded monopole antennas operating at 75 MHz in terms of their radiated power concerning the frequency, the far-field directivity of the electric field, and the effect of each design parameter on the far-field radiation power. According to the results, folding a monopole antenna multiple times increases its effective length, making this antenna a suitable candidate for applications where the antenna height is restricted. Additionally, the ground-to-wire separation has the biggest effect on radiated power. In both single-fold and two-fold cases, doubling the ground-to-wire separation increased the radiated power by 0.2 W compared to the other models with the same number of folds. As for the challenges, the impedance mismatch between the source and antenna causes a significant amount of power reflection; hence, suitable impedance matching is required to reduce reflected power. Full article

In this study, we investigate the damping phenomena acting on piezoelectrically driven MEMS oscillators. Three different geometrical shapes of MEMS oscillators are presented, including cantilevers, bending oscillators, and paddle oscillators. An analytical model for their resonance frequencies is derived. The bending modes of these micro-oscillator structures are characterized regarding their resonance frequency and their quality factor as a function of the ambient pressure in a nitrogen atmosphere as well as the dependence on the distance to a neighboring plate representing a geometrical boundary (e.g., to the package or to the mounting). The investigations cover a pressure range from 10⁻³ mbar up to 900 mbar and a gap width from 150 µm to 3500 µm. Consequently, a Knudsen number range over six orders of magnitude from 100 to 10⁻⁴ is covered. The measurement data are evaluated with a generalized damping model consisting of four parts representing the individual damping mechanisms (intrinsic, molecular, transitional, and viscous). The evaluated parameters are analyzed as a function of the resonance frequency and the gap width. The data reveal an exponential growing saturation behavior, which is determined by two characteristic lengths, being correlated with the viscous and the thermal boundary layer thickness, respectively. This leads to an estimation of the strength and of the range of the damping effect just by calculating the boundary layer thicknesses given by the resonance frequency and the gas properties. From these results, we gain fundamental insights on the viscous and transitional damping mechanisms as well as on the intrinsic losses. In conclusion, a basic concept is provided to reduce the damping of micro-oscillator bending modes and thus increase the quality factor. Additionally, the results are supported by finite element simulations revealing the temperature and pressure distribution within the gap. Full article

When the concentration of a gas exceeds the equilibrium concentration in a liquid, the gas–liquid system is referred as a supersaturated system. The supersaturation can be achieved by either changing the pressure and/or temperature of the system. The gas from a supersaturated liquid escapes either through bubble nucleation that usually occurs on solid surface and/or gas diffusion through the gas–liquid interface. The bubble nucleation requires a minimum threshold supersaturation. A waiting time is required to observe whether the applied supersaturation is sufficient to initiate bubble nucleation. When the supersaturation is not sufficient to cause bubble nucleation, some or all of the supersaturated gas may diffuse out from the liquid through the gas–liquid interface before further reducing the pressure in order to increase the supersaturation. In this article, using Fick’s second law of diffusion and Henry’s law, an analytical method is proposed to estimate the level of supersaturations generated in three gas–liquid systems at different step-down pressures. Characteristic times of the gas–liquid systems were estimated to validate whether the waiting times used in this study are in accordance with the semi-infinite diffusion model used to estimate the supersaturations generated. Full article

This work presents the development of a decision-making strategy for fulfilling the power and heat demands of small residential neighborhoods. The decision on the optimal operation of a microgrid is based on the model predictive control (MPC) rolling horizon. In the design of the residential microgrid, the new approach different technologies, such as photovoltaic (PV) arrays, micro-combined heat and power (micro-CHP) units, conventional boilers and heat and electricity storage tanks are considered. Moreover, electricity transfer between the microgrid components and the national grid are possible. The MPC problem is formulated as a mixed integer linear programming (MILP) model. The proposed novel approach is applied to two case studies: one without electricity storage, and one integrated microgrid with electricity storage. The results show the benefits of considering the integrated microgrid, as well as the advantage of including electricity storage. Full article

Powders and their mixtures are elemental for many industries (e.g., food, pharmaceutical, mining, agricultural, and chemical). The properties of the manufactured products are often directly linked to the particle properties (e.g., particle size and shape distribution) of the utilized powder mixtures. The most straightforward approach to acquire information concerning these particle properties is image capturing. However, the analysis of the resulting images often requires manual labor and is therefore time-consuming and costly. Therefore, the work at hand evaluates the suitability of Mask R-CNN—one of the best-known deep learning architectures for object detection—for the fully automated image-based analysis of particle mixtures, by comparing it to a conventional, i.e., not machine learning-based, image analysis method, as well as the results of a trifold manual analysis. To avoid the need of a laborious manual annotation, the training data required by Mask R-CNN are produced via image synthesis. As an example for an industrially relevant particle mixture, endoscopic images from a fluid catalytic cracking reactor are used as a test case for the evaluation of the tested methods. According to the results of the evaluation, Mask R-CNN is a well-suited method for the fully automatic image-based analysis of particle mixtures. It allows for the detection and classification of particles with an accuracy of 42.7% for the utilized data, as well as the characterization of the particle shape. Also, it enables the measurement of the mixture component particle size distributions with errors (relative to the manual reference) as low as −2±5 for the geometric mean diameter and −6±5% for the geometric standard deviation of the dark particle class of the utilized data, as well as −8±4% for the geometric mean diameter and −6±2% for the geometric standard deviation of the light particle class of the utilized data. Source code, as well as training, validation, and test data publicly available. Full article

Metallic Ni shows high activity for a variety of hydrogenation reactions due to its intrinsically high capability for H₂ activation, but it suffers from low chemoselectivity for target products when two or more reactive functional groups are present on one molecule. Modification by other metals changes the geometric and electronic structures of the monometallic Ni catalyst, providing an opportunity to design Ni-based bimetallic catalysts with improved activity, chemoselectivity, and durability. In this review, the hydrogenation properties of these catalysts are described starting from the typical methods of preparing Ni-based bimetallic nanoparticles. In most cases, the reasons for the enhanced catalysis are discussed based on the geometric and electronic effects. This review provides new insights into the development of more efficient and well-structured non-noble metal-based bimetallic catalytic systems for chemoselective hydrogenation reactions. Full article

This paper presents the results of testing the adhesion of geopolymer coatings and varnishes with ceramic additives to concrete and steel substrates. The measurement method used and described in this article was the pull-off method. The pull-off method test provides an easy way to evaluate the degree of adhesion of coatings to metal surfaces. The pull-off device provides values for the peel stress, which not only allows a quick determination of the adhesion of the coating to the substrate, but also makes it easier to compare the adhesion of several coatings to each other. However, this method requires appropriate preparation, so an attempt was made to determine its suitability for geopolymer layers. The results of testing the adhesion of a geopolymer layer to a geopolymer substrate and a concrete substrate are presented. As a result of this study, a higher adhesion strength of the geopolymer layer to the geopolymer substrate was found in comparison to geopolymer coatings applied on conventional concrete. Adhesion tests were also conducted for steel substrates to which both geopolymer and acrylic lacquer were applied. Full article

The paper formulates the foundations of a recently developed approach, named the method of fundamental components, intended for constructing heuristic solutions in problems of electromagnetic diffraction, for the first time. The difference between the new method and the known heuristic approaches lies in the application of an adjustment procedure that increases the accuracy. The possibility of the mentioned method for obtaining new results is illustrated with the help of the author’s previously published works. The advantages of the new method in constructing high-speed solvers and in the physical interpretation of numerical solutions are shown. Full article

Material extrusion additive manufacturing (MEAM) is an advanced manufacturing method that produces parts via layer-wise addition of material. The potential of MEAM to prototype lattice structures is remarkable, but restrictions imposed by manufacturing processes lead to practical limits on the form and dimension of structures that can be produced. For this reason, such structures are mainly manufactured by selective laser melting. Here, the capabilities of fused filament fabrication (FFF) to produce custom-made lattice structures are explored by combining the 3D printing process, including computer-aided design (CAD), with the finite element method (FEM). First, we generated four types of 3D CAD scaffold models with different geometries (reticular, triangular, hexagonal, and wavy microstructures) and tunable unit cell sizes (1–5 mm), and then, we printed them using two nozzle diameters (i.e., 0.4 and 0.8 mm) in order to assess the printability limitation. The mechanical behavior of the above-mentioned lattice scaffolds was studied using FEM, combining compressive modulus (linear and nonlinear) and shear modulus. Using this approach, it was possible to print functional 3D polymer lattice structures with some discrepancies between nozzle diameters, which allowed us to elucidate critical parameters of printing in order to obtain printed that lattices (1) fully comply with FFF guidelines, (2) are capable of bearing different compressive loads, (3) possess tunable porosity, and (3) overcome surface quality and accuracy issues. In addition, these findings allowed us to develop 3D printed wrist brace orthosis made up of lattice structures, minimally invasive (4 mm of thick), lightweight (<20 g), and breathable (porosity >80%), to be used for the rehabilitation of patients with neuromuscular disease, rheumatoid arthritis, and beyond. Altogether, our findings addressed multiple challenges associated with the development of polymeric lattice scaffolds with FFF, offering a new tool for designing specific devices with tunable mechanical behavior and porosity. Full article

Pavement structures cover vast areas of urban cities and non-urban roads and play a key role in daily commuting functionality and economic development; therefore, they must be conserved against any distress. The rutting problem, being a major distress to the pavement structure, must be solved and dealt with in order to preserve its value. One way of solving this dilemma is by using geo-grids within the pavement structure. A geo-grid is a synthetic material usually made from polymers with different thicknesses and stiffnesses. This paper investigates the effects of geo-grids on reducing the rutting occurrence through adding a layer of geo-grid with certain properties at different levels of the pavement structure. We also investigate, the result of the added geo-grid material to the developed vertical stresses within the pavement cross-section. This investigation is conducted by constructing a 3-D finite elements-based (FE) model of a pavement cross-section using ANSYS software; student version R1 2021. The FE-based model is validated by comparing its numerical predictions with the experimental results acquired from an accelerated large-scale paved model. The results show that the deeper the geo-grid is positioned, the more significant the rutting resistance is observed due to the stiffness of the geo-grid bearing the tensile force until a certain depth. Moreover, noticeable stress reduction is seen in the developed vertical compressive stresses below the loading area resisted by the geo-grid. Full article