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  • 1
    In: Materials, MDPI AG, Vol. 15, No. 21 ( 2022-10-26), p. 7513-
    Abstract: In this study, the effect of waste glass on the mechanical properties of concrete was examined by conducting a series of compressive strength, splitting tensile strength and flexural strength tests. According to this aim, waste glass powder (WGP) was first used as a partial replacement for cement and six different ratios of WGP were utilized in concrete production: 0%, 10%, 20%, 30%, 40%, and 50%. To examine the combined effect of different ratios of WGP on concrete performance, mixed samples (10%, 20%, 30%) were then prepared by replacing cement, and fine and coarse aggregates with both WGP and crashed glass particles. Workability and slump values of concrete produced with different amounts of waste glass were determined on the fresh state of concrete, and these properties were compared with those of plain concrete. For the hardened concrete, 150 mm × 150 mm × 150 mm cubic specimens and cylindrical specimens with a diameter of 100 mm and a height of 200 mm were tested to identify the compressive strength and splitting tensile strength of the concrete produced with waste glass. Next, a three-point bending test was carried out on samples with dimensions of 100 × 100 × 400 mm, and a span length of 300 mm to obtain the flexure behavior of different mixtures. According to the results obtained, a 20% substitution of WGP as cement can be considered the optimum dose. On the other hand, for concrete produced with combined WGP and crashed glass particles, mechanical properties increased up to a certain limit and then decreased owing to poor workability. Thus, 10% can be considered the optimum replacement level, as combined waste glass shows considerably higher strength and better workability properties. Furthermore, scanning electron microscope (SEM) analysis was performed to investigate the microstructure of the composition. Good adhesion was observed between the waste glass and cementitious concrete. Lastly, practical empirical equations have been developed to determine the compressive strength, splitting tensile strength, and flexure strength of concrete with different amounts of waste glass. Instead of conducting an experiment, these strength values of the concrete produced with glass powder can be easily estimated at the design stage with the help of proposed expressions.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 2
    In: Materials, MDPI AG, Vol. 15, No. 20 ( 2022-10-17), p. 7234-
    Abstract: Joining immiscible materials such as copper and stainless steel together is a significant concern due to distinct mechanical and metallurgical properties across the joint line, such as melting points, the coefficient of linear thermal expansion, and thermal conductivity. The joint properties of copper to stainless steel welds are in great demand for various mechanical components of the international thermonuclear experimental reactor, ultra-high vacuum system, plan wave linear-accelerator or linac structure, and heat exchanger. These dissimilar-metals joints offer excellent flexibility in design and production, leading to a robust structure for many cutting-edge applications. Hence, the present article reviews the copper to stainless steel joining mechanism under different solid-state processing conditions. The present understanding says that defect-free strong joints between the dissimilar metals are systematically possible. Apart from this understanding, the authors have identified and highlighted the gaps in the research exploration to date. Moreover, a sustainable methodology to achieve a desirable weld of copper to stainless steel depends on favorable processing conditions.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 3
    In: Polymers, MDPI AG, Vol. 14, No. 23 ( 2022-12-03), p. 5291-
    Abstract: The applications of carbon fiber reinforced polymer composites (CFRPCs) in aerospace, automotive, electronics and lab-on-chip devices require precise machining processes. Over the past decade, there have been numerous attempts to machine CFRPCs using both traditional and unconventional machining techniques. However, because of their limitations, these methods have not gained widespread acceptance. In the present research investigation, Electrochemical Discharge Machining (ECDM) process has been employed to produce micro-holes on CFRPC. The experimental strategy was scheduled using L9 orthogonal array keeping applied voltage, electrolyte concentration and inter-electrode gap as input parameters. The material removal rate (MRR) and overcut were selected as output parameters. The technique for order preference by similarity to the ideal solution (TOPSIS) methodology was executed for multi-response optimization. The overcut and MRR of machined samples improved from 150 µm to 48 µm and 2.232 mg/min to 2.1267 mg/min correspondingly while using the optimum parametric settings of the TOPSIS approach. The shape of drilled micro-holes produced by the TOPSIS process is indicative of a machined surface of superior quality, with a reduction in the number of micro-cracks and a diameter that is uniform.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2527146-5
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  • 4
    In: Coatings, MDPI AG, Vol. 11, No. 12 ( 2021-12-15), p. 1542-
    Abstract: Worker safety is one of the main aspects to be taken into account in any activity carried out at work. When we talk about the safety of the worker at activities carried out at height, the condition and characteristics of the personal protective equipment against falling from a height are one of the main causes of work accidents resulting in serious injuries or death. Carabiners are the main components of the safety system; their role is to connect the other components of the system or to make the connection between the system and the anchor point. Therefore, to be used safely, the carabiners’ material must have high corrosion resistance in different environments. This paper is part of a complex study that aims to improve the corrosion properties of carbon steel used in the manufacture of carabiners. Previous studies have shown that the corrosion resistance of carbon steel in various corrosive environments has been improved by the deposition of different types of phosphate layers, as well as other subsequently deposited layers. The aim of this paper is to study the galvanic corrosion evaluation between different galvanic couples (duralumin-coated samples, aluminium bronze-coated samples, and carbon steel-coated samples) tested in three different corrosive media. Moreover, the study approaches for the first time the galvanic corrosion of systems that can be formed between the materials used in the manufacture of carabiners. Accordingly, it was observed that, overall, the samples coated with a Zn phosphate layer exhibited the best performance in all the corrosive environments (saltwater and fire extinguishing solution).
    Type of Medium: Online Resource
    ISSN: 2079-6412
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2662314-6
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  • 5
    In: Bioengineering, MDPI AG, Vol. 9, No. 10 ( 2022-09-27), p. 510-
    Abstract: The purpose of this research is to emphasize the importance of mental health and contribute to the overall well-being of humankind by detecting stress. Stress is a state of strain, whether it be mental or physical. It can result from anything that frustrates, incenses, or unnerves you in an event or thinking. Your body’s response to a demand or challenge is stress. Stress affects people on a daily basis. Stress can be regarded as a hidden pandemic. Long-term (chronic) stress results in ongoing activation of the stress response, which wears down the body over time. Symptoms manifest as behavioral, emotional, and physical effects. The most common method involves administering brief self-report questionnaires such as the Perceived Stress Scale. However, self-report questionnaires frequently lack item specificity and validity, and interview-based measures can be time- and money-consuming. In this research, a novel method used to detect human mental stress by processing audio-visual data is proposed. In this paper, the focus is on understanding the use of audio-visual stress identification. Using the cascaded RNN-LSTM strategy, we achieved 91% accuracy on the RAVDESS dataset, classifying eight emotions and eventually stressed and unstressed states.
    Type of Medium: Online Resource
    ISSN: 2306-5354
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2746191-9
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  • 6
    In: Applied Sciences, MDPI AG, Vol. 11, No. 17 ( 2021-08-25), p. 7802-
    Abstract: Phosphate coatings are one of the most important methods in preventing metal corrosion, especially iron alloys. The high interest in this method for industrial applications is mainly due to the low costs associated with the phosphating solution component and technological process. Considering this aspect and the advantages offered to the materials (corrosion resistance, good adhesion, wear resistance), this study evaluates the potential of using the phosphate coating method in health and safety applications. Therefore, the deposition of a layer of zinc phosphate on the steel surface used in the manufacture of components for personal protective equipment was approached. Firefighters, during rescue/evacuation operations, use protective equipment for fall arrest, whose accessories (hooks, carabiners) are made of steel. Due to the low corrosion resistance property of carbon steel, these accessories must be replaced frequently. This paper aims to analyze the possibility of improving the corrosion resistance of carbon steel in a fire extinguishing solution. Accordingly, the electrochemical behavior of two different types of coatings was studied by electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). In the literature, different corrosion evaluating methods or systems have been considered, and up until now, there has been no previous study to have approached the corrosive behavior of C45, phosphate C45, and painted phosphate C45 immersed in fire extinguishing solution.
    Type of Medium: Online Resource
    ISSN: 2076-3417
    Language: English
    Publisher: MDPI AG
    Publication Date: 2021
    detail.hit.zdb_id: 2704225-X
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  • 7
    In: Materials, MDPI AG, Vol. 15, No. 24 ( 2022-12-18), p. 9050-
    Abstract: This study was carried out to investigate the effect of the diamond-shaped Interlocking Chain Plastic Bead (ICPB) on fiber-reinforced fly ash-based geopolymer concrete. In this study, geopolymer concrete was produced using fly ash, NaOH, silicate, aggregate, and nylon66 fibers. Characterization of fly ash-based geopolymers (FGP) and fly ash-based geopolymer concrete (FRGPC) included chemical composition via XRF, functional group analysis via FTIR, compressive strength determination, flexural strength, density, slump test, and water absorption. The percentage of fiber volume added to FRGPC and FGP varied from 0% to 0.5%, and 1.5% to 2.0%. From the results obtained, it was found that ICBP fiber led to a negative result for FGP at 28 days but showed a better performance in FRGPC reinforced fiber at 28 and 90 days compared to plain geopolymer concrete. Meanwhile, NFRPGC showed that the optimum result was obtained with 0.5% of fiber addition due to the compressive strength performance at 28 days and 90 days, which were 67.7 MPa and 970.13 MPa, respectively. Similar results were observed for flexural strength, where 0.5% fiber addition resulted in the highest strength at 28 and 90 days (4.43 MPa and 4.99 MPa, respectively), and the strength performance began to decline after 0.5% fiber addition. According to the results of the slump test, an increase in fiber addition decreases the workability of geopolymer concrete. Density and water absorption, however, increase proportionally with the amount of fiber added. Therefore, diamond-shaped ICPB fiber in geopolymer concrete exhibits superior compressive and flexural strength.
    Type of Medium: Online Resource
    ISSN: 1996-1944
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2487261-1
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  • 8
    In: Diagnostics, MDPI AG, Vol. 12, No. 11 ( 2022-11-11), p. 2758-
    Abstract: The presence of laryngeal disease affects vocal fold(s) dynamics and thus causes changes in pitch, loudness, and other characteristics of the human voice. Many frameworks based on the acoustic analysis of speech signals have been created in recent years; however, they are evaluated on just one or two corpora and are not independent to voice illnesses and human bias. In this article, a unified wavelet-based paradigm for evaluating voice diseases is presented. This approach is independent of voice diseases, human bias, or dialect. The vocal folds’ dynamics are impacted by the voice disorder, and this further modifies the sound source. Therefore, inverse filtering is used to capture the modified voice source. Furthermore, the fundamental frequency independent statistical and energy metrics are derived from each spectral sub-band to characterize the retrieved voice source. Speech recordings of the sustained vowel /a/ were collected from four different datasets in German, Spanish, English, and Arabic to run the several intra and inter-dataset experiments. The classifiers’ achieved performance indicators show that energy and statistical features uncover vital information on a variety of clinical voices, and therefore the suggested approach can be used as a complementary means for the automatic medical assessment of voice diseases.
    Type of Medium: Online Resource
    ISSN: 2075-4418
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2662336-5
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  • 9
    In: Coatings, MDPI AG, Vol. 13, No. 6 ( 2023-06-01), p. 1029-
    Abstract: This paper aims to study the possibility of improving the chemical and surface characteristics of the Ti6Al4V alloy by depositing phosphate layers on its surface. Accordingly, an innovative phosphating solution was developed and used in a chemical conversion process to obtain Ca–Zn phosphate layers on the base material surface. Moreover, the chemical composition of the phosphate solution was chosen considering the biocompatibility of the chemical elements and their possibility of contributing to the formation of phosphate compounds. The obtained layer was characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and potentiodynamic polarization tests. The wetting of the Ca–Zn sample surface was also investigated using water and two liquids similar to body fluids, namely, Ringer and Dulbecco solutions. According to the surface energy study, the polar component is almost two times larger compared with the dispersive one. The SEM and EDS tests revealed a uniformly coated surface with intercalated crystals leading to a rough surface. Furthermore, the XRD results showed not only the presence of hopeite and scholzite but also of phosphophyllite. By the vibrations of the PO4−3 groups, the FTIR test confirmed the presence of these phases. The potentiodynamic tests revealed that the samples coated with the Ca–Zn phosphate layer present better corrosion resistance and a lower corrosion rate compared with the uncoated ones.
    Type of Medium: Online Resource
    ISSN: 2079-6412
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2662314-6
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  • 10
    In: Polymers, MDPI AG, Vol. 15, No. 13 ( 2023-06-22), p. 2785-
    Abstract: This manuscript presents an experimental investigation of the friction and wear properties of poly (methyl methacrylate) (PMMA) nanocomposites reinforced with functionalized multi-walled carbon nanotubes (MWCNTs). The aim of this study is to evaluate the potential of MWCNTs as a reinforcement material for enhancing the tribological performance of PMMA. Three types of multi-walled carbon nanotubes, i.e., pristine, hydroxyl functionalized, and carboxyl functionalized, were utilized in this study. The nanocomposite samples were prepared by dispersing varying concentrations of MWCNTs (0.1 wt.%, 0.5 wt.%, and 1 wt.%) within the PMMA matrix via a 3D mixing approach, followed by injection molding/compression molding. The resulting nanocomposite films were characterized using scanning electron microscopy (SEM) to observe the dispersion of MWCNTs within the PMMA matrix. The friction and wear tests were conducted using a pin-on-disk tribometer under dry sliding conditions. The effects of functionalization and MWCNT content on the tribological behaviors of the nanocomposites were analyzed. The nanocomposites exhibited lower friction coefficients and reduced wear rates compared to pure PMMA. The lowest friction coefficient and wear rate were achieved at an optimum MWCNT loading of 0.5 wt.%. It was further revealed that the amount of MWCNT reinforcement, average load, and track diameter significantly affect the coefficient of friction (COF) and rate of wear. The COF and wear rate are best at a filler loading of 0.5 wt.%, a 20 Kg load, and 90 mm. The improved tribological performance of the MWCNT-reinforced PMMA nanocomposites can be attributed to the effective transfer of load between the MWCNTs and the PMMA matrix, as well as the reinforcement effect of the MWCNTs. The MWCNTs acted as reinforcing agents, enhancing the mechanical properties and wear resistance of the nanocomposites.
    Type of Medium: Online Resource
    ISSN: 2073-4360
    Language: English
    Publisher: MDPI AG
    Publication Date: 2023
    detail.hit.zdb_id: 2527146-5
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