Kermanshah University of Technology

Existing high step-up dc–dc converters suffer from various issues, including limited voltage gain, high voltage stress on semiconductors, using a large number of components, and high current ripple. To solve these issues simultaneously, some of the new converters have been proposed recently, which must be improved by the new ones. Hence, this article presents an ultrahigh step-up converter with the objective of maximizing the potential use of renewable energy sources (RES). The suggested converter employs a quadratic boost converter (QBC), a switched capacitor network, and a three-winding coupled inductor to produce a substantial gain in voltage while ensuring continuous current in the input and a common ground between load and source. The voltage stress on semiconductor components has been minimized by the placement of the coupled inductor. Comparative analysis showcases the converter’s superior voltage gain capability compared to the currently introduced step-up dc-dc converters. The converter requires the minimum inductance in order to remain capable of supporting the load with minimal input current ripple, ultimately reducing power loss. The validity of the theoretical analysis of the converter is subsequently proven through experimentation on a prototype with a rated value of 200Woutput power, 20V input voltage, and 400V output voltage.

Several approaches have been proposed to improve oil-contaminated soil remediation. However, the role of zeolite, a safe, clean, economical, and environmentally friendly material, in removing crude oil (CO) from contaminated soils remains unclear. This paper addresses this gap with respect to CO-contaminated sands (COCS) and aims to assess zeolite’s capability as a geo-environmentally adaptable material to mitigate the adverse impacts of oil pollution on sandy soils. The cyclic simple shear behavior and chemical analysis of coarse and fine-grain silicate sands are investigated and compared in response to CO contamination. Clean sand specimens were prepared with 60% relative density, whereas COCS specimens were prepared using a 6% crude oil contamination level. This study examines the impact of CO contamination and the use of an environmentally friendly stabilizer through simple shear tests (under static and cyclic conditions), consolidation experiments, and Fourier-transform infrared spectroscopy (FTIR). Optimal pollution adsorption was achieved by adding 6% zeolite to fine-grained sand, resulting in a 31.61% increase in the shear modulus index and an 18.70% increase in the friction angle index. Using 8% zeolite improved the shear modulus and friction angle indexes in coarse-grained sand by 21.69% and 11.83%, respectively. FTIR results showed a 45% and 59% enhancement in coarse and fine sands, respectively, indicating the positive role of zeolite in stabilizing COCS through pollutant adsorption. The superior performance of zeolite in fine-grained compared with coarse-grained sand is justified by its higher specific surface area and porous surface.

Sakli et al. previously studied the propagation characteristics of wave modes in a metallic circular waveguide filled with anisotropic metamaterial [ Int. J. Microw. Wirel. Technol. 9 , 805–813 (2017)]. They derived and analyzed the wave equation and dispersion relations for TE z and TM z modes (i.e., TE and TM waves related to the z -axis) within the waveguide. However, they did not verify whether the system actually supports these TE z and TM z waves. This work aims to investigate that issue. Our findings indicate that, in general, a metallic circular waveguide filled with anisotropic metamaterial cannot support the propagation of TE z and TM z waves. Consequently, the results presented by Sakli et al. are incorrect.

The aim of this study was to utilize thermodynamic laws analysis to optimize the geometric parameters of a double-tube heat exchanger that incorporates water-graphene nanofluid. The heat exchanger was outfitted with novel type of twisted conical fins on the tube side and ribs on the annular side. The realizable \text{k}-\upvarepsilon model with enhanced wall treatment function was utilized to simulate a counter-current flow in which nanofluid passes on the tube side and water passes on the annular side in a turbulent regime. The heat exchanger’s design parameters, including the number of twisted conical fins, number of ribs on the annular side, pitch, and height of the elliptical ribs were investigated. Multi-objective optimization was then conducted to achieve the dual objectives of maximizing heat transfer and minimizing both friction coefficient and entropy generation. To determine objective functions based on decision variables in the multi-objective optimization, the group method of data handling was employed. Through a parametric study, it was found that increasing the pitch, number, and height of ribs on the annular side results in enhanced heat exchange between the two fluids and an increase in entropy and friction coefficient. Conversely, increasing the number of conical fins leads to increased heat transfer and friction coefficient while decreasing entropy production on the tube side. According to the obtained results, in the average values of other variables of the problem, in the changes of conical fins from 1 to 2 compared to 2 to 3, the values of the changes in the overall heat transfer coefficient and the friction coefficient were 1.9 times and 1.4 times higher, respectively, while it is 2.4 times less in total entropy production, which shows the greater effect of changing the number of conical fins from 1 to 2 compared to 2 to 3, as well as a greater effect on the overall entropy production. The optimal state for the given decision variables was specified using the multi-objective optimization method. The results of the three-objective optimization revealed that the optimal state was achieved when the pitch, number of ribs, and fins parameters were set to approximately the middle of their range of variation. Furthermore, the most optimal state possible was achieved with the minimum rib height. The optimal geometry leads to entropy production 15.7% more than the lowest entropy production and 73.9% less than the highest entropy production.

This study introduces two 4D and 5D laser chaotic systems, including the regularized Prabhakar fractional derivative with incommensurate parameters, and investigates their properties and complex dynamics. The system’s chaotic vibration is then controlled via a feedback control approach. Furthermore, we demonstrate that the parameters of the regularized Prabhakar fractional derivative have a significant impact on the stability and chaotic behavior of the systems. The numerical simulation results show that systems with the regularized Prabhakar fractional derivative are more stable than the integer order systems or the fractional systems with the Caputo fractional derivative. Furthermore, two identical regularized Prabhakar fractional laser chaotic systems are synchronized by the design of control laws.

Recent studies indicate poor air quality inside the subway system due to the successive generation and accumulation of particles. Many of these particles are iron-containing airborne wear particles generated by the abrasion of brake pads. In the present study, the concentration distribution of wear particles emitted from train brake pads during train braking is investigated. Due to the unsteady three-dimensional turbulent flow caused by the train movement inside the large geometry of the subway system, this numerical modeling requires a high computational cost, especially when the Lagrangian method, which tracks every single particle, is used. So, applying the less expensive Eulerian method, which considers the particle phase as a continuum, is preferable. However, the feasibility of using the Eulerian approach instead of the Lagrangian one should be examined, especially for the large particles emitted from a moving body inside a train-induced turbulent flow field. Therefore, in the present work, the predictions of particle concentration obtained through these two methods are compared. The predictions of the Eulerian method are more continuous and uniform, while those of the Lagrangian method, which is based on the accumulation of individual particles, are more scattered. The results show that the Eulerian method can provide reasonable predictions while maintaining computational efficiency.

The addition of low-loading content of nanofillers may improve the material properties of polymer-based nanocomposites. This improvement directly corresponds to the density of well-dispersed nanofillers in the matrix. However, for higher nanofiller loadings, the nanocomposites' material properties not only may not be improved but also may be degraded due to agglomeration. This complex phenomenon, where nanofillers tend to form agglomerates with the enhancement of volume fraction, poses significant challenges in materials science and nanotechnology. It has been proven that agglomerations hinder the performance of the nanocomposites and thwart the unique properties of nanofillers in most aspects. Graphene, one of the most used nanofillers, plays a remarkable role in nanotechnology. Therefore, the key focus of the current review is to provide insight into the impact of agglomeration on the various material properties such as tensile, flexural, fracture, fatigue, thermal, electrical, and barrier characteristics of the polymer nanocomposites reinforced by graphene-based structures. A comprehensive review of the factors leading to the agglomeration of graphene in the nanocomposites was presented. It was concluded that agglomeration could be a barrier to developing polymer-based nanocomposites, and the challenges of controlling the nanofiller agglomerations were discussed in depth, highlighting the issue's complexity.

This article introduces a three-port dc–dc converter including two input sources with continuous input current; one of them is a bidirectional port to ensure continuous charging and discharging of battery storage. The proposed converter boosts voltage with a higher gain than the references, which use more components. The voltage stress on the diodes and the size of the main inductor are also compared to other converters, demonstrating the superior properties of the proposed converter. In addition, the article contains new kinds of comparisons to review multiport converters from other point of views like performance limitations and number of operation modes. The converter is designed in a way to comprise a common ground between the sources and the load. The possibility of operation in battery-alone mode enhances its reliability and certainty for various standalone applications of renewable energy systems. To validate the feasibility and effectiveness of the proposed converter, an experimental prototype with a nominal power of 300 W was developed. The conducted experiments involve dynamic performances of the converter during sudden changes in the load and switching between different modes. The experimental results confirm the functionality and practicality of the proposed converter.

A new expandable, non-isolated, high step-up threeport DC-DC converter (TPC), with two inputs and one output, which includes a bidirectional port for charging and discharging energy storage, is presented in this paper. The proposed TPC is compatible with expanding the number of inputs and becoming a multi-input converter (MIC). Also, it has a high voltage gain, an appropriate number of components, low voltage stress on the semiconductors, and low input current ripple. In addition, the paper includes new kinds of comparison criteria to assess multiinput converters from various perspectives, such as performance limitations and quality. The design of the converter incorporates beneficial characteristics, such as continuous input current and a common ground between the energy sources and the load. It also has the capability to operate in battery-alone mode and under unbalanced conditions, accommodating different powers and voltage levels of the input sources. Moreover, the employed switching strategy enables effective control over the input current of the sources as well as the output voltage. Various operating modes and steady-state analysis have been discussed to validate the advantages of the proposed TPC. Finally, a 300W laboratory prototype is designed to verify the performance of the proposed TPC under sudden changes and during mode transitions.

This paper introduces an innovative 2 × 2 MIMO, Multi-Input Multi-Output, antenna working in the sub-Terahertz (THz) band for 6G, 6-Generation, communications (0.1–1.2 THz). This antenna was designed with main metal octagonal patches and parasitic graphene elements, providing pattern reconfigurable antenna for Single-Input Single-Output (SISO) and MIMO applications. In the YZ-plane, aforementioned antenna illustrates a tunable pattern (0°, +70°, −70°) for SISO in three distinct states. In the XZ-plane, it obtains a versatile MIMO function with a controllable pattern (0°, ±20°, ±45°, ±75°) across four states, simultaneously. The adaptability of the radiation pattern is originated from changing graphene conductivity through biasing. In addition, a graphene metasurface was applied as an absorber, moderately improving isolation between 2 antenna elements, minimizing interference, and enhancing the overall system capability. The proposed schematization achieves a significant isolation up to −35 dB within the MIMO antenna’s operational frequency band. Moreover, the MIMO antenna touches a maximum gain of 9.5 dBi, maximum impedance bandwidth of approximately 91% during different states, 10 dBi Diversity Gain, and 2.62×10−7 ECC in the resonance frequency, which demonstrates novelty designing, remarkable pros, and broad applications in the landscape evolution of 6G communication networks.

In recent years, laminated composites reinforced with natural fibers have extensively used in the various industries. One of the most important failure modes of laminated composite materials is translaminar fracture under different loading conditions. In this research, the effect of temperature on the translaminar critical strain energy release rate (CSERR) of the composites reinforced with cotton fibers was investigated. The cotton/epoxy samples were placed at different temperature conditions of 30, 0, and -30 °C. The translaminar CSERR values of cotton/epoxy laminated composites were obtained under pure mode I, mixed mode I/II with two different loading angles, and pure mode II loading conditions. To calculate the translaminar CSERR based on experimental results, numerical modeling was also performed. Besides, a modified version of Mixed Mode Fracture Envelope criterion was proposed to predict the mixed mode I/II translaminar fracture behavior of the cotton/epoxy laminated composites at the mentioned temperatures. The results showed that lowering the temperature has a great impact on the translaminar CSERR. It was also concluded that the change in the temperature had the greatest effect on the value of the mode I translaminar CSERR. Moreover, as the temperature decreased from 30 to 0 and -30 °C, the value of the mode I translaminar CSERR decreased around 80 and 90%, respectively.

Liquefaction, a vital issue in geotechnical engineering, is often due to cyclic stress leading to the effective stress in the soil mass reaching zero. This phenomenon depends on several aspects, including the soil type. Most previous research has focused on the liquefaction behavior of silicate sands, which significantly differ from carbonate sands in terms of static and dynamic resistance. Therefore, this study investigates the liquefaction behavior of clean Bushehr carbonate sand (CBCS), crude oil-contaminated Bushehr carbonate sand (COCBCS), and stabilized crude oil-contaminated Bushehr carbonate sand (SCOCBCS). The stabilization process uses three additives, i.e., Nano clay (NC), Portland cement (PC), and silicon dioxide (SD). The study finds that the addition of 4% NC has the highest impact on stabilizing the liquefaction of Bushehr carbonate sand, causing an 8.5-fold increase in the number of cycles required for liquefaction to occur compared to when the sand is contaminated with crude oil. Among the additives, 2% SD is the least effective, resulting in only a 2-fold increase in dynamic resistance. SEM and XRD results show that the structure and particle size of the sands do not change when mixed with different percentages of crude oil. The chemical analysis results indicate that PC (due to its chemical composition) can more effectively alter the characteristics of treated samples. However, due to higher surface area, NC stabilizes the liquefaction potential of oil-contaminated Bushehr carbonate sands more efficiently than other stabilizer agents.

This paper aims to employ the Darboux transformation (DT) to discover the interaction solutions of the Zakharov equation (Eq. ( 1.2 ) for [Formula: see text]). Through partial degradation of eigenvalues, interaction solutions of the model are constructed on the basis of high-order breather solutions. The study derives interaction solutions involving breather and b-positon solutions through partial degradation of eigenvalues ([Formula: see text]). Further, interaction solutions comprising breather and lump solutions are obtained through partial double degradation of eigenvalues ([Formula: see text]). Then, several interaction solutions containing b-positon and lump solutions are extracted through mixed degradation of eigenvalues ([Formula: see text] and [Formula: see text]). In particular, the dynamic evolution characteristics of these solutions are studied. It is believed that these studies make a significant contribution to the understanding of the Zakharov equation and its possible applications in physics.

Effective decision-making in urban water infrastructure optimization, particularly in sustainable urban drainage systems (SuDS), hinges on navigating complex multi-objective problems. This study addresses the challenge of sparse Pareto-fronts in many-objective SuDS design, often caused by algorithmic limitations and the intricate objective function interactions, impacting the availability of diverse design alternatives for decision-makers. To tackle these challenges, this research proposes a novel framework that integrates advanced data imputation and surrogate modeling techniques. The framework uses artificial intelligence methods to populate the sparse regions by replicating the Pareto-front structure, predicting decision variables to guide further simulations and find efficient solutions without repeated optimization runs. The methodology is validated through a SuDS design case study located in Ann Arbor, Michigan. Following the initial optimization, sparse regions were identified in four of the eight objective functions. Using the proposed framework, 32 new and efficient SuDS designs were introduced into the sparse regions without additional optimization, enhancing the uniformity of the Pareto front. This study enhances decision support tools in urban flood management by increasing the informativeness of design alternatives available to planners and engineers.

Objective To assess the effect of beverages on the color change of glazed monolithic zirconia ceramic. Material and Methods This in vitro study evaluated 18 A2-shade disc-shaped monolithic zirconia specimens measuring 10 x 2 mm. All specimens were sintered, coated with a thin layer of glaze paste, heated in a vacuum furnace, and were subjected to 5000 thermal cycles at 5 and 55 °C. The specimens were then randomized into three groups (n=6) for immersion in orange juice, tea, and distilled water for 135 minutes/day for 24 days and incubated. The color of specimens was measured before and after immersion by a spectrophotometer, and the color change (∆E) was calculated according to the CIE L*a*b* color space. Data were analyzed using one-way ANOVA and Tukey’s post-hoc test (alpha=0.05). Results All three groups experienced a color change after immersion (p<0.05). The ∆E was maximum in tea (2.05±1.04) and minimum in orange juice (0.81±0.57). Significant differences were noted between orange juice and tea (p<0.001), and distilled water and tea (p<0.001) in ∆L, and orange juice and tea (p=0.023), and distilled water and tea (p=0.030) in ∆E. Conclusion The results indicated that tea caused maximum color change and maximum reduction in lightness (L*) in glazed monolithic zirconia ceramic; however, the color change was within the clinically acceptable range (∆E<3.7). Keywords: Dental Materials; Ceramics; Color; Spectrophotometry

Periodic inspection of power transformers is important to prevent possible failures in power systems. One effective approach is transformer oil analysis. In recent years, the need for a fast, accurate and in situ method has been increased significantly. This research has employed laser-induced breakdown spectroscopy (LIBS) to analyze transformer oil and investigate its aging. For this purpose, changes in the intensity of molecular emissions (C2, CN and OH) and their correlation with aging processes have been used. Spectral investigation showed that Cu lines had been added to the spectra of aged samples. Temperature and electron density of plasma have calculated. Additionally, the principal component analysis (PCA) method was used to check and compare the overall spectra. Finally, the results of Gas Chromatography (GC) and Acid Number (AN) tests were given to confirm the age of the samples.

A study of the propagation characteristics of electromagnetic waves in a hyperbolic metamaterial-filled circular coaxial waveguide, with the inner and outer perfect electric conductor (PEC) surfaces, was reported before by Bhardwaj et al. [J. Lightwave Technol. 37, 3064 (2019)]. They showed that the TEz and TMz (i.e., TE and TM waves related to the z-axis) are the eigen modes of the mentioned system, and concluded that radial hyperbolicity (ϵr < 0, ϵz ≃ ϵφ > 0) is more advantageous than axial hyperbolicity (ϵz < 0, ϵr ≃ ϵφ > 0) for near-field coupling effects. However, the study by Bhardwaj et al. has a fundamental error, where for the case (ϵr < 0, ϵz ≃ ϵφ > 0) the proposed system cannot support the propagation of the TEz and TMz waves, and therefore in this case the results derived by Bhardwaj et al. are incorrect.