Materials

In this study, a homemade uniaxial strain pressure cell was designed to be directly used in the standard magnetometers whereby the magnetic properties of samples subjected to a uniaxial strain and magnetic field were characterized. Its feasibility has been demonstrated by the uniaxial strain control of the phase transition and magnetocaloric effect in Ni₄₀Co₁₀Mn₄₀Sn₁₀ (NCMS) alloys. With the assistance of a uniaxial strain of ~0.5%, the cooling temperature span of NCMS alloys is broadened by 2 K, and the refrigeration capacity under a 3 T magnetic field change increases from 246 to 277 J/kg. This research provides not only direct experimental assistance for the tuning of phase transition by the uniaxial strain but also possibilities for studying the coupled caloric effect in first-order phase transition materials under a combined uniaxial strain and magnetic field by the thermodynamic analysis. Full article

Coal mining waste in the form of coal gangue (CG) was established recently as a potential fill material in earthworks. To ascertain this potential, this study forecasts the strength and California Bearing Ratio (CBR) characteristics of chemically stabilized CG by deploying two widely used artificial intelligence approaches, i.e., artificial neural network (ANN) and random forest (RF) regression. In this research work, varied dosage levels of lime (2, 4, and 6%) and gypsum (0.5, 1, and 1.5%) were employed for determining the unconfined compression strength (UCS) and CBR of stabilized CG mixes. An experimental study comprising 384 datasets was conducted and the resulting database was used to develop the ANN and RF regression models. Lime content, gypsum dosage, and 28 d curing period were considered as three input attributes in obtaining three outputs (i.e., UCS, unsoaked CBR, and soaked CBR). While modelling with the ANN technique, different algorithms, hidden layers, and the number of neurons were studied while selecting the optimum model. In the case of RF regression modelling, optimal grid comprising maximal depth of tree, number of trees, confidence, random splits, enabled parallel execution, and guess subset ratio were investigated, alongside the variable number of folds, to obtain the best model. The optimum models obtained using the ANN approach manifested relatively better performance in terms of correlation coefficient values, equaling 0.993, 0.995, and 0.997 for UCS, unsoaked CBR and soaked CBR, respectively. Additionally, the MAE values were observed as 45.98 kPa, 1.41%, and 1.18% for UCS, unsoaked CBR, and soaked CBR, respectively. The models were also validated using 2-stage validation processes. In the first stage of validation of the model (using unseen 30% of the data), it was revealed that reliable performance of the models was attained, whereas in the second stage (parametric analysis), results were achieved which are corroborated with those in existing literature. Full article

Glutamine plays a significant role in several basic metabolic processes and is an important regulator of heat shock protein response. The present work is focused on the analysis of the thermal response of aqueous solutions of Glutamine and aqueous solutions of Glutamine in the presence of Trehalose by means of infrared absorption technique. The performed study shows how in the case of a multicomponent system, characterized by a huge number of spectral contributions whose assignment are questionable, the Spectral Distance (SD) and the Cross Wavelet Correlation (XWT) approaches are able to furnish explanatory parameters that can characterize the variations in the spectra behaviour, which is an efficient tool for quantitative comparisons. With this purpose, the analysis has been performed by evaluating the SD and the XWT parameters for the whole investigated spectral range, i.e., 4000–400 cm⁻¹, for scans collected as a function of temperature in the range 20 °C ÷ 60 °C both for Glutamine/Water compounds and for Glutamine /Water/Trehalose mixtures. By means of these analyses, it is found that in aqueous solutions of Glutamine, with respect to aqueous solutions of Glutamine in the presence of Trehalose, the SD and XWT temperature trends follow a linear behaviour where the angular coefficient for Glutamine /Water/Trehalose compounds are lower than that of the Glutamine-Water system in both cases. The obtained findings suggest that Trehalose stabilizes Glutamine against heat treatment. Full article

In this paper, the optimization of laser-MAG hybrid welding parameters of 10CrNi3MoV ship steel was developed. Using the Box-Behnken Design (BBD) model in Response Surface Methodology (RSM) and taking laser power, welding speed and welding current as response factors, the design matrix was completed and verified by experiment. The regression model associated with welding parameters was established by measuring the response indices, such as penetration, tensile strength and impact absorption energy. Through the model check, it was found that the accuracy of penetration and tensile strength of the model was high, and the optimized parameters were as follows: laser power (P) = 3700 W, welding speed (V) = 0.8 m/min, wire feeding speed (Vs) = 7 m/min. On the premise of meeting mechanical performance inspection standards, the maximum penetration was 8 mm. Full article

The purpose of this paper is to develop a constitutive description and to numerically simulate a propagating instability phenomenon called the Portevin–Le Chatelier (PLC) effect, which is observed for metallic materials. It manifests itself by moving plastic shear bands in the sample and serrations in the stress–strain diagram. In this paper, the PLC is modeled by geometrically non-linear thermo-visco-plasticity with the hardening function of the Estrin–McCormick type to reproduce a serrated response. To regularize softening, which in this model comes from thermal, geometrical and strain-rate effects, the viscosity and heat conductivity are incorporated. Plasticity description can additionally include degradation of the yield strength, and then the model is enhanced by higher-order gradients. Simulations are performed using AceGen/FEM. Two tensioned specimens are tested: a rod and a dog-bone sample. The first specimen is used for general verification. The results obtained for the second specimen are compared with the experimental results. Studies for different values of model parameters are performed. The results of the simulations are in good agreement with the experimental outcome and the sensitivity to model parameters is in line with the expectations for the pre-peak regime. In the presented tests, the gradient enhancement does not significantly influence the results. Full article

Multiple compression tests on rock-like samples of pre-existing cracks with different geometries were conducted to investigate the strength properties and crack propagation behavior considering multi-crack interactions. The progressive failure process of the specimens was segmented into four categories and seven coalescence modes were identified due to different crack propagation mechanisms. Ultimately, a mechanical model of the multi-crack rock mass was proposed to investigate the gradual fracture and damage evolution traits of the multi-crack rock on the basis of exploring the law of the compression-shear wing crack initiation and propagation. A comparison between theory and experimental results indicated that the peak strength of the specimens with multiple fractures decreased initially and subsequently increased with the increase in the fissure inclination angles; the peak strength of specimens decreased with the increase in the density of fissure distribution. Full article

To develop a mechanistic-empirical pavement design system for Norwegian conditions, this paper evaluates the influence of the adoption of different models and shifting techniques on the determination of dynamic modulus master curves of asphalt mixtures. Two asphalt mixture types commonly used in Norway, namely Asphalt Concrete (AC) and Stone Mastic Asphalt (SMA) containing neat bitumen and polymer-modified bitumen, were prepared by the roller compactor, and their dynamic moduli were determined by the cyclic indirect tensile test. The dynamic modulus master curves were constructed using the standard logistic sigmoidal model, a generalized logistic sigmoidal model and the Christensen–Anderson–Marasteanu model. The shifting techniques consisted of log-linear, quadratic polynomial function, Arrhenius, William–Landel–Ferry and Kaelble methods. The absolute error, normalised square error and goodness-of-fit statistics encompassing standard error ratio and coefficient of determination were used to appraise the models and shifting methods. The results showed that the standard logistic sigmoidal model and the Williams–Landel–Ferry equation had the most suitable fits for the specimens tested. The asphalt mixtures containing neat bitumen had a better fit than the ones containing polymer-modified bitumen. The Kaelble equation and log-linear equation led to similar results. These findings provide a relevant recommendation for the mechanistic-empirical pavement design system. Full article

Embossing is a converting process in which the surface of a tissue paper sheet is changed under high pressure, allowing different functions. In this work, the authors intend to study how the embossing pressure affects the main properties of tissue paper, using a laboratory embossing system. An optimum pressure was achieved at 2.8 bar to this embossing laboratory set-up. The effect of pressure when densifying the paper sheet gives it a gain in mechanical strength but no differences in terms of liquid absorbency. The two embossing patterns present different behaviors but both evidence losses in mechanical and softness properties. On the other hand, the finite element method (FEM) does not show clear evidence of how the pressure affects the paper strength. For the deco die, it is possible to observe that the amount of yielding is slightly higher for lower pressure (2.4 bar), but this plasticity state parameter is very similar for 2.8 bar and 3.2 bar. For the micro die, FEM simulations of the manufacturing pressure do not show a considerable impact on the amount of plasticity state of the material; only for 3.2 bar, it shows a change in the pattern of the plasticity state of the paper during the embossing processes. In the end, to achieve a final product with excellent quality, it is important to make a compromise between the various properties. Full article

Smart textiles have become a promising area of research for heating applications. Coatings with nanomaterials allow the introduction of different functionalities, enabling doped textiles to be used in sensing and heating applications. These coatings were made on a piece of woven cotton fabric through screen printing, with a different number of layers. To prepare the paste, nanomaterials such as graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (CNTs) were added to a polyurethane-based polymeric resin, in various concentrations. The electrical conductivity of the obtained samples was measured and the heat-dissipating capabilities assessed. The results showed that coatings have induced electrical conductivity and heating capabilities. The highest electrical conductivity of (9.39 ± 1.28 × 10⁻¹ S/m) and (9.02 ± 6.62 × 10⁻² S/m) was observed for 12% (w/v) GNPs and 5% (w/v) (CNTs + GNPs), respectively. The sample with 5% (w/v) (CNTs + GNPs) and 12% (w/v) GNPs exhibited a Joule effect when a voltage of 12 V was applied for 5 min, and a maximum temperature of 42.7 °C and 40.4 °C were achieved, respectively. It can be concluded that higher concentrations of GNPs can be replaced by adding CNTs, still achieving nearly the same performance. These coated textiles can potentially find applications in the area of heating, sensing, and biomedical applications. Full article

Surface roughening is an important material surface treatment technique, and it is particularly useful for use in secondary electron yield (SEY) suppression on metal surfaces. Porous structures produced via roughening on coatings have been confirmed to reduce SEY, but the regulation strategy and the influence of process parameters both remain unclear in the practical fabrication of effective porous structures. In this paper, the effect of the surface morphology of porous coatings on the SEY of aluminum alloy substrates was studied. Surface characterization and SEY measurements were carried out for samples with a specific process technique on their surfaces. An exponential fitting model of the correlation between surface roughness and the peak values of SEY curves, ${\delta }_m$, was summarized. Furthermore, an implementation strategy to enable low surface SEY was achieved from the analysis of the effect of process parameters on surface morphology formation. This work will aid our understanding of the effect of the irregular surface morphology of porous coatings on SEY, thereby revealing low-cost access to the realization of an easy-to-scale process that enables low SEY. Full article

This paper presents a method for the synthesis of ammonium alginate by interphase gas-solid reaction. It was confirmed by FTIR ATR spectroscopy analysis that a full substitution of acid groups by ammonium groups on the surface of powdered alginic acid was performed. Comparative studies on the properties of ammonium alginate solutions obtained by interphase reaction with those prepared by the classical method of dissolving alginic acid in an ammonia solution showed that the rheological properties of the solutions from these two derivatives do not differ significantly. Moreover, it was shown that aqueous solutions of ammonium alginate are more stable over time than solutions of sodium alginate. It was confirmed that ammonium alginate and sodium alginate are typical polyelectrolytes, as the addition of a low molecular weight electrolyte to their solutions resulted in a decrease in viscosity. Full article

Textile production has been steadily increasing for a few decades and, as a result, the amount of industrial textile waste is also increasing. This waste can be reused as raw material to produce new functional composites. Such materials can be used for special purposes with varying combinations of physical and chemical properties by using polymers modified with thin semiconductive or electrically conductive layers of binary inorganic compounds. In this paper, a study of the possibilities of altering the properties of synthetic fiber conductivity by modification with copper selenide is presented. A two-step adsorption/diffusion method was used for the copper selenide layer forming on the surface of the fibers. The treatment process was repeated cyclically. To evaluate the morphological properties of Cu_xSe treated fibers, scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) were performed. The study showed that the chosen modification method is more suitable for PA and PAN fibers. Dense layers of copper selenides were successfully formed on their surface, which significantly reduced their electrical resistance. Full article

(1) Background: The phenomenon of ankylosis of the dental elements has led clinicians to think that properly treated dentin and cement may be a potential graft for alveolar ridge augmentation. Currently, there are no studies in the literature able to histomorphometrically compare the healing patterns of an autogenous dentin particulate graft with the association, or not, of resorbable membranes. The aim of this pilot study is to histologically compare bone after an alveolar ridge augmentation using an autogenous dentin particulate graft with and without a resorbable collagen membrane. (2) Methods: this clinical trial enrolled six patients with defects requiring bone augmentation. Two procedures were performed in all six adult human patients in order to perform a study–control study: in Group 1, a ridge augmentation procedure with an autogenous dentin particulate graft and a resorbable collagen membrane was performed, and, in Group 2, an alveolar ridge preservation without a membrane was performed at the same time (T0). At 4 months, a biopsy of the bone tissues was performed using a 4 mm trephine bur in order to perform a histomorphometric analysis. (3) Results: The histomorphometric analysis demonstrated that Group 1 presented 45% of bone volume, 38% of vital bone, and 7% of residual graft. On the contrary, membrane-free regenerative procedures demonstrated 37% of bone volume, 9% of vital bone, and 27% of non-resorbed graft. In all cases, the regenerated bone allowed the insertion of implants with a standard platform, and no early failures were recorded. (4) Conclusions: Autogenous dentin particulate grafts seem to work best when paired with a membrane. Full article

Polyurethane cement (PUC) is now commonly used in the reinforcement of old bridges, which exhibit various issues such as poor toughness, temperature-sensitive mechanical properties, and brittle failure. These problems can lead to the failure of the reinforcement effect of the PUC on old bridges in certain operating environments, leading to the collapse of such reinforced bridges. In order to alleviate these shortcomings, in this study, the toughness of PUC is improved by adding polyvinyl alcohol (PVA) fiber, carbon fiber, and steel fiber. In addition, we study the change law of the flexural strength of PUC between −40 °C and +40 °C. The control parameters evaluated are fiber type, fiber volume ratio, and temperature. A series of flexural tests and scanning electron microscope (SEM) test results show that the flexural strength first increases and then decreases with the increase in the volume-doping ratio of the three fibers. The optimum volume-mixing ratios of polyvinyl alcohol (PVA) fiber, carbon fiber, and steel fiber are 0.3%, 0.04% and 1%, respectively. Excessive addition of fiber will affect the operability and will adversely affect the mechanical properties. The flexural strength of both fiber-reinforced and control samples decreases with increasing temperature. Using the flexural test results, a two-factor (fiber content, temperature) BP neural network flexural strength prediction model is established. It is verified that the model is effective and accurate, and the experimental value and the predicted value are in good agreement. Full article

Triboscopy focuses on the analysis of the temporal evolution of a tribological system, combining local and time-resolved information, most commonly the evolution of friction. In this work, this technique is applied on measurements, which were carried out with a custom-built ultra-high vacuum tribometer in ball-on-disc configuration. Based on these experiments, an extended classification to distinguish different triboscopic features is suggested, depending on the persistence in both track position and time: Uniform, Global, Local, and Sporadic. Further, a filter technique for quantifying triboscopic data regarding this classification is introduced. The new and improved triboscopic techniques are applied to various dry friction measurements of hydrogen-free carbon coatings under varying humidity and pressure. The resulting specific triboscopic features are correlated to wear phenomena, such as counter body coating abrasion, inhomogeneities in the wear track, non-uniform track wear, stick-slip and debris in the contact area, demonstrating the increased analysis and monitoring capabilities when compared to conventional friction curves and wear track images. Full article

Incorporating biodegradable reinforcement, such as wood particles, into rigid polyurethane foams (RPUFs) is among the alternatives to reduce their environmental impact. This study aims to assess the effect of different wood particles as reinforcement in RPUFs. Reinforced rigid polyurethane foams are synthesized with milled wood particles of various forms and sizes and commercial polyol and isocyanate. The effect of fiber treatments and mechanical stirring on foams’ properties is also studied. Additional tests on polyisocyanurate foams (PIR) were undertaken to assess the effect of reinforcement on their properties. Mechanical properties are measured to investigate the impact of wood particle reinforcement on the foam. Confocal microscopy and Fourier-transform infrared spectroscopy (FTIR) showed the interaction between the wood fibers and the matrix. Despite the adhesion observed for some fibers, most of the cell walls of RPUFs were punctured by the rigid wood fibers, which explained the decrease in the compressive strength of the composites for manually mixed foams. Mechanical stirring proved to be an efficient method to enhance the reinforcement power of untreated fibers. RPUF foams’ properties showed similar changes when untreated wood flour was introduced to the formula, increasing compressive strength significantly. Full article

Recently, self-powered health monitoring systems using a wearable thermoelectric generator (WTEG) have been rapidly developed since no battery is needed for continuous signal monitoring, and there is no need to worry about battery leakage. However, the existing materials and devices have limitations in rigid form factors and small-scale manufacturing. Moreover, the conventional bulky WTEG is not compatible with soft and deformable tissues, including human skins or internal organs. These limitations restrict the WTEG from stabilizing the thermoelectric gradient that is necessary to harvest the maximum body heat and generate valuable electrical energy. This paper summarizes recent advances in soft, flexible materials and device designs to overcome the existing challenges. Specifically, we discuss various organic and inorganic thermoelectric materials with their properties for manufacturing flexible devices. In addition, this review discusses energy budgets required for effective integration of WTEGs with wearable biomedical systems, which is the main contribution of this article compared to previous articles. Lastly, the key challenges of the existing WTEGs are discussed, followed by describing future perspectives for self-powered health monitoring systems. Full article

The influence of load on the cellulose microfibrils of single cells or thin wood foils is known. It can decrease the cellulose microfibril angles and, in turn, increase the stiffness. However, this modification of a piece of wood, which is made up of multiple cells, is unknown. The aim of this research was to study the effect of tensile creep on the longitudinal stiffness of radiata pine wood. The modulus of elasticity of each specimen was determined before and after being subjected to tensile creep. The samples were loaded at 1170 N and 1530 N for 20 min at 70 °C. The load was determined as a function of a percentage of the force at the proportional limit. The moduli of elasticity before and post-tensile creep showed no effect on the stiffness of wood at the macroscopic level, but neither were there damage to the cell structure. It can be assumed that there are changes at the microscopic level, but they are not enough to be reflected at the macro scale. It is also challenging to achieve the modifications that occur at the level of a single cell or in thin wood foils; however, the implications of this would be favorable for the development of stronger wood-based products. Full article

With the development of new concrete technology, high-strength concrete has been used worldwide. In particular, more economic benefits can be achieved by applying high-strength concrete-filled steel tube (HSCFST) columns in the concrete core walls of super high-rise buildings. A constitutive relation with high applicability for high-strength materials with different strength grades is proposed. Based on this constitutive model, a brick element model of 181 sets of axially compressed square HSCFST members is established and experimentally verified. The effects of the concrete strength, diameter-to-thickness ratio, and steel yield strength on the axial compressive capacities of these members were investigated based on finite element calculation results. The results showed that with an increase in the concrete strength, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 60%, 24%, 44%, and 21% at most, respectively. Additionally, as the steel yield strength increased, the ultimate bearing capacities of CS-CC, HS-HC, HS-CC, and CS-HC stub column members increased by 8.8%, 5.1%, 8.5%, and 5.2%, respectively, Hence, material strength has the greatest impact on CS-CC and HS-CC. The confinement effect of the square steel tube on the concrete weakens as the strength grade of steel or concrete increases. Notably, the confinement effect of steel tube on the concrete is strongest in CS-CC and weakest in the CS-HC. In addition, the confinement coefficients of square HSCFST stub columns with different combinations of concrete and steel strengths were analyzed. Based on the superposition principle in the ultimate state, a practical axial compressive capacity calculation formula for three types of square HSCFSTs is established. Compared with existing major design code formulas, the proposed formula is more accurate and concise and has a clear physical meaning. Full article