Mohd Syahir Anwar Hamzah, Nadirul Hasraf Mat Nayan, Soon Chin Fhong
et al.
Nerve tissue engineering requires biomaterials that provide mechanical strength, biocompatibility, and an optimal microenvironment for cell attachment and proliferation. Electrospun polymeric scaffolds have gained attention due to their structural similarity to the extracellular matrix. However, their inherent brittleness and limited bioactivity necessitate further enhancement. This study investigates the effects of incorporating a polyvinyl alcohol/collagen/halloysite nanotube (PVA/Col/HNT) hydrogel on the physicochemical properties of polyvinylidene fluoride/polyvinyl alcohol (PVDF/PVA) electrospun mats to improve their suitability for nerve regeneration applications. The hydrogel was integrated onto the electrospun matrices using casting and freeze-thawing techniques. The resultant composites were characterized for their morphological, mechanical, and biological properties. Field emission scanning electron microscopy revealed a uniform distribution and interconnectivity between the electrospun mat and hydrogel layer, supported by Fourier transform infrared spectroscopy spectra indicating strong hydrogen bonding interactions. Atomic force microscopy demonstrated reduced surface roughness (Ra: 5.3 nm electrospun surface, 41.9 nm hydrogel surface) compared to single-layer electrospun mats (Ra: 192.5 nm), promoting better cell attachment and proliferation. Mechanical testing showed a significant increase in tensile strength (1.762 MPa) and Young's modulus (39.612 MPa) while maintaining high elongation at break (316.253%), ensuring flexibility and durability. The scaffold's piezoelectric properties further enhanced its potential for nerve regeneration. In vitro biocompatibility assays using human fibroblast cells confirmed increased cell adhesion and proliferation, highlighting the suitability of the PVA/Col/HNT hydrogel-infused PVDF/PVA mats for soft tissue engineering. This study underscores the composite's potential in advancing nerve regeneration therapies.
Mechanical engineering and machinery, Mechanics of engineering. Applied mechanics
A novel precipitate-strengthened Co–Cr–Ni medium-entropy alloy with a pure “FCC + L12” dual-phase structure is developed by adding a high concentration (6 at.%) of Al and Ti elements. After aging heat treatment at 700 °C for 4 h, the hierarchical L12 phases, composed of primary large-sized L12 phases (∼70 nm) and secondary L12 particles (∼14 nm), are achieved. The designed alloy featuring hierarchical L12 phases exhibits excellent strength-ductility combinations and strain-hardening ability, properties that are much improved over their counterparts with homogeneous dispersed L12 phases (∼13 nm) and without L12 phases. Especially, the yield strength (1320 MPa), ultimate tensile strength (1886 MPa), and average strain-hardening rate (5.15 GPa) are obtained in the alloy with hierarchical L12 precipitates deformed at cryogenic temperature. The Orowan bypass mechanism of the primary L12 phases, along with the shearing mechanism of the secondary L12 phases, collectively contributes to the exceptional strength of the alloy with hierarchical L12 precipitates. The penetration of dislocations and stacking faults (SFs) in the primary L12 phases, combined with hetero-deformation-induced (HDI) hardening attributed to these hierarchical L12 precipitates, may be a key factor in improving strain-hardening properties of the alloy.
Based on comprehensive interrelated mathematical and graphical-analytical models, including 3D cut layers and simulation of contact, strain, force, and thermal processes during gear hobbing friction forces, heat fluxes, and temperature on the teeth of the hob surface are investigated. Various physical phenomena are responsible for their wear: friction on contact surfaces and thermal flow. These factors act independently of each other; therefore, the worn areas are localized in different active parts of the hob. Friction causes abrasive wear and heat fluxes result in heat softening of the tool. Intense heat fluxes due to significant friction, acting on areas of limited area, lead to temperatures exceeding the critical temperature on certain edges of the high-speed cutter. Simulation results enable identification of high-temperature areas on the working surface of cutting edges, where wear is caused by various reasons, and make it possible to select different methods of hardening these surfaces. To create protective coatings with maximum heat resistance, it is advisable to use laser technologies, electro spark alloying, or plasma spraying, and for coatings that provide reduction of friction on the surfaces – formation of diamond-containing layers with minimum adhesion properties and low friction coefficient on the corresponding surfaces.
We proposed a method to display an intermediate visual texture by spatial mixing. In addition to color information, the visual texture is an important element that characterizes the nature of an object’s surface. While the system to display various color information has well matured in engineering, there is no method to reproduce visual textures in ambient light. In our method, the matte and glossy surfaces are used as “primary visual textures”, and an intermediate visual texture is displayed by spatially mixing the primary visual textures. In this paper, we first quantified the visual texture of an object’s surface based on measured intensities of scattered and reflected lights. Next, based on the quantification, we evaluated spatially mixed surfaces consisting of two primary visual textures, an acrylic plate and a holed sheet of drawing paper, by changing the area proportion of the two primary visual textures. Finally, a sensory evaluation showed significant differences between each intermediate visual texture, and the results corresponded to a trend in the optical evaluation. This study illustrates that visual textures could be quantified based on the intensity of scattered and reflected light and reveals the applicability of our method to the display for intermediate visual texture.
Multi-body dynamics is used to calculate the physical quantities required for component design, such as calculating the dynamic response of mechanical components and the time history of dynamic loads. Advances in analysis software, including DADS, ADAMS, RecurDyn, and DAFUL, have made it possible to easily calculate dynamic responses by defining relationships between components and operating environments from 3D modeling on user-created components. However, when the understating of dynamic analysis is lacking, it is difficult to apply multi-body dynamics analysis in the design process, and it is difficult to analyze the acquired response data. In this study, we developed an automatic code to derive equations of motion in the matrix format and calculate dynamic responses of multi-body systems using GNU Octave, a free high level language. In particular, the process of defining matrices and vectors such as inertia matrix, stiffness matrix, and external force vector concerning the degrees of freedom of components by using Euler-Lagrange equations is shown to understand the structure and process of dynamic analysis. The code application by explaining how to use the code in a different mechanical system is also shown to help understand the usage method for who wants to study Multi-body dynamics.
When the biomass gasifier is connected with a gas engine system directly, tar should be removed from the syngas to prevent the engine from breaking down. A downdraft packed bed gasifier has the advantage for low tar emission because the syngas passes through the char gasification zone downstream of the reactor, where tar compounds can be trapped and decomposed. Then, objective of this study is to confirm the tar decomposition behaviors inside the downdraft packed bed reactor. Woody biomass gasification experiments were carried out, using an auto-thermal downdraft packed bed gasifier. The reactor’s height and inner diameter were 1000mm and 100mm, respectively. Black pine pallets were continuously fed into the reactor from the top. The gasifying agent was air, which was introduced into the reactor at the air-fuel equivalent ratio of 0.49. The packed bed height was kept to be constant at 600mm. The reactor has eleven thermo-couples and eleven sampling ports at the wall along the flow direction. They were used for measurements of temperature profiles and gas compositions in the reactor. Micro-GC was used for the measurement of N2, O2, CO, CO2 and H2, and FIDGC was used for other hydrocarbons. In some ports among them, tar in syngas was also sampled via dichloromethane scrubbing in ice-bath, and analyzed for molecular weight distributions of tar compounds by TOF-MS. As a result, tar and larger hydrocarbons were confirmed to be generated in the upstream, and then decomposed downstream inside the downdraft reactor.
Mechanical engineering and machinery, Mechanics of engineering. Applied mechanics
Alex Sagalovych, Viktor Popov, Vladislav Sagalovych
et al.
Розроблена дуплексна технологія Avinit шляхом плазмового прецизійного азотування Avinit N і подальшого нанесення поліфункціонального антифрикційного покриття Avinit С на поверхні, що труться і сприймають силові навантаження.
Досліджено вплив дуплексного процесу на розміри деталей, вивчені властивості азотованого шару і параметри покриттів Avinit.
Дуплексна технологія Avinit забезпечує нанесення міцнозчеплених, високоякісних поліфункціональних антифрикційних зносостійких покриттів Avinit С на складнопрофільних деталях.
Із застосуванням розробленої дуплексної технології Avinit виготовлена дослідна партія сепараторів для муфти вільного ходу головного редуктора гвинтокрила.
Всі параметри сепаратора, виготовленого за дуплексною технологією Avinit, повністю відповідають технічним, металургійним і металографічним вимогам КД (товщина і мікроструктура азотованого шару, відсутність крихкості, товщина і твердість покриття, збереження геометричних параметрів з точністю до 0,5 мкм).
Сепаратор муфти вільного ходу з покриттям Avinit успішно пройшов випробування в складі головного редуктора гвинтокрилу на натурному стенді.
Як показали результати випробувань, застосування розробленої дуплексної технології Avinit забезпечує повну відсутність фретинг-зносу робочих поверхонь, звичайного для серійних сепараторів.
Mohammad Nasir Uddin, Monir Uddin, Ibrahim Khalil
et al.
This research was aimed to evaluate the potential of biosorption technique in more realistic conditions that appeal to the industry by exploiting locally available biosorbents such as jute stick powder (JSP), an agricultural product, for the removal of toxic Pb(II), Cr(III) and Cd(II) ions from wastewater. Fourier transform infrared spectroscopy (FTIR) and Scanning electron micrographs (SEM) analysis proved that the surface of biosorbent was porous, with heterogeneous structures that contained high internal spaces. The removal efficiencies of the mixture of the target metals by JSP were optimized with respect to pH, initial metal concentration, shaking time and biomass dose. Biosorption performance of JSP in multiple metal systems was above 90 percent adsorption for tested metal ions. Biomass regeneration efficiencies up to 98% were achieved using acid as eluent. Sorption performance of the JSP as biosorbent was examined by classical adsorption equilibrium isotherms, kinetics in batch systems, and dynamic continuous flow studies. Batch sorption studies revealed that pseudo-first, pseudo-second-order, and Langmuir isotherm models were suitable to describe the metals sorption kinetics and equilibrium, respectively.
Electrical engineering. Electronics. Nuclear engineering, Mechanical engineering and machinery
In the present paper, thermal decomposition and crystal researches of synthesized potassium sulphamate (PS) and potassium dinitramide (KDN) crystals were studied using differential scanning calorimetry/ thermal gravimetry (DSC/TG) and scanning electron microscope (SEM) techniques, respectively. Initially, PS crystals were synthesized using sulphamic acid and potassium hydroxide pellets. Afterwards, PS crystals were used for synthesizing potassium dinitramide (KDN) crystals by the nitration of PS in sulfuric and nitric acid mixture. One sample of PS was used for studying DSC/TG curves, while three samples of KDN crystals were used for the studying DSC/TG curves. The three samples of KDN crystals which were used in the present studies are, a) stored KDN (1 month), b) stored KDN (2 months), and c) washed KDN. All the obtained DSC/TG curves of three KDN crystals are dissimilar to each other, and the probable reasons for this dissimilarity are discussed in the manuscript. For further clarifications, TG curve of KN was compared with the TG curves of three samples of KDN used in the present study. It was observed that, while storage, KDN slowly converts into KN with some rate which gradually changes the physical and chemical properties of KDN.
In this paper the detailed OAT (one-at-a-time) sensitivity analysis of a nonlinear fire truck suspension system is carried out with numerical simulation. As output to measure sensitivity the RMS of acceleration was chosen, which can be calculated with numerical simulations easily. The degree of sensitivity was measured with a sensitivity index and based on it sensitivity Fuzzy-sets were established. The membership of each parameter to the Fuzzy sets is calculated and based on it, it was determined which parameters are the most sensitive. With the presented results it is shown that the proposed method is suitable for testing mathematical models as well.
Engineering (General). Civil engineering (General), Mechanics of engineering. Applied mechanics
Miguel Martínez-Comesaña, Lara Febrero-Garrido, Enrique Granada-Álvarez
et al.
The Heat Loss Coefficient (HLC) characterizes the envelope efficiency of a building under in-use conditions, and it represents one of the main causes of the performance gap between the building design and its real operation. Accurate estimations of the HLC contribute to optimizing the energy consumption of a building. In this context, the application of black-box models in building energy analysis has been consolidated in recent years. The aim of this paper is to estimate the HLC of an existing building through the prediction of building thermal demands using a methodology based on Machine Learning (ML) models. Specifically, three different ML methods are applied to a public library in the northwest of Spain and compared; eXtreme Gradient Boosting (XGBoost), Support Vector Regression (SVR) and Multi-Layer Perceptron (MLP) neural network. Furthermore, the accuracy of the results is measured, on the one hand, using both CV(RMSE) and Normalized Mean Biased Error (NMBE), as advised by AHSRAE, for thermal demand predictions and, on the other, an absolute error for HLC estimations. The main novelty of this paper lies in the estimation of the HLC of a building considering thermal demand predictions reducing the requirement for monitoring. The results show that the most accurate model is capable of estimating the HLC of the building with an absolute error between 4 and 6%.
Hoang-Thien Luu, Roberto G. A. Veiga, Nina Gunkelmann
It has long been known that iron undergoes a phase transformation from body-centered cubic/<inline-formula> <math display="inline"> <semantics> <mi>α</mi> </semantics> </math> </inline-formula> structure to the metastable hexagonal close-packed/<inline-formula> <math display="inline"> <semantics> <mi>ε</mi> </semantics> </math> </inline-formula> phase under high pressure. However, the interplay of line and planar defects in the parent material with the transformation process is still not fully understood. We investigated the role of twins, dislocations, and Cottrell atmospheres in changing the crystalline iron structure during this phase transformation by using Monte Carlo methods and classical molecular dynamics simulations. Our results confirm that embryos of <inline-formula> <math display="inline"> <semantics> <mi>ε</mi> </semantics> </math> </inline-formula>-Fe nucleate at twins under hydrostatic compression. The nucleation of the hcp phase is observed for single crystals containing an edge dislocation. We observe that the buckling of the dislocation can help to nucleate the dense phase. The crystal orientations between the initial structure <inline-formula> <math display="inline"> <semantics> <mi>α</mi> </semantics> </math> </inline-formula>-Fe and <inline-formula> <math display="inline"> <semantics> <mi>ε</mi> </semantics> </math> </inline-formula>-Fe in these simulations are <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mfenced open="{" close="}"> <mn>110</mn> </mfenced> <mrow> <mi>b</mi> <mi>c</mi> <mi>c</mi> </mrow> </msub> <mrow> <mo>|</mo> <mo>|</mo> </mrow> <msub> <mfenced open="{" close="}"> <mn>0001</mn> </mfenced> <mrow> <mi>h</mi> <mi>c</mi> <mi>p</mi> </mrow> </msub> </mrow> </semantics> </math> </inline-formula>. The presence of Cottrell atmospheres surrounding an edge dislocation in bcc iron retards the development of the hcp phase.
Actual problems of the government regulation of the investment activity on the regional level of management are investigated. Availability of the goal-oriented method and ways of developing regional investment policy is considered.
The review of methods of calculation and optimization of die forging processes is submitted. The scheme of direct and inverse mathematical simulation of metal forming and methods realization of calculation are considered. On concrete examples the principles and methods of the calculation of optimum original and intermediate blanks for forgings being produced by die forging processes are shown.
The aim of this paper is to investigate the physical properties of thermoplastic sugar palm starch/agar (TPSA) blend when incorporated with seaweed. The ratio of starch, agar, and glycerol for TPSA was maintained at 70:30:30. Seaweed with various contents (10, 20, 30, and 40 wt.%) were mixed with TPSA matrix via melt mixing before compression were molded into 3 mm plate at 140oC for 10 minutes. The prepared laminates were characterized for moisture absorption, water absorption, thickness swelling, water solubility, and density. The results showed that increasing seaweed loading from 0 to 40 wt% has led to a drop in moisture content from 6.50 to 4.96% and 9% reduction of the density. TPSA matrix showed 52.5% water uptake and 32.3% swelling whereas TPSA/seaweed composites (40 wt% loading) showed 97% water uptake and 74.8% swelling respectively. Higher water solubility was also shown by TPSA/seaweed composites (57 wt%) compared to that of the TPSA matrix (26 wt%). After 16 days of storage, the equilibrium moisture content for TPSA and TPSA/seaweed (40 wt% loading) were 23.2 and 25.2% respectively. In conclusion, TPSA/seaweed composites show good environmental friendly characteristics as a renewable material. In future, the properties of this material can be further improved by hybridization with more hydrophobic fillers for better resistance against water.
Mechanical engineering and machinery, Mechanics of engineering. Applied mechanics
In this study, the effects of radiation and convection heat transfer in a radial porous fin are considered. The geometry considered is that of a rectangular profile fin. The porous fin allows the flow to infiltrate through it and solid-fluid interaction takes place. This study is performed using Darcy’s model to formulate the heat transfer equation. The thermal conductivity is assumed to be a function of temperature. The effects of the natural convection parameter Nc , radiation parameter Nr and thermal conductivity parameter m on the dimensionless temperature distribution and heat transfer rate are discussed. The results suggest that the radiation transfers more heat than a similar model without radiation
The purpose of this study is to elucidate flame propagation behavior under the application of uniform and non-uniform electric fields by using a constant volume vessel. Two electrodes are attached to the ceiling and the bottom of the combustion chamber and electric fields are applied in the direction of the chamber's vertical axis. A Nd:YAG laser is used to apply laser-induced breakdown for igniting the mixture at the center of the combustion chamber. A homogeneous propane-air mixture is supplied at three equivalence ratios of 0.7, 1.0 and 1.5 and ignited under atmospheric pressure and room temperature. Under a uniform electric field, the premixed flame rapidly propagates both upward and downward, forming a cylindrically shaped flame front. The maximum combustion pressure decreases with increasing input voltage because the flame front reaches the chamber wall rapidly and the heat loss to electrodes increases. However, the combustion duration is little affected by the input voltage. In a non-uniform electric field, the flame propagation velocity in the downward direction increases. Combustion is markedly enhanced when the input voltage is larger than 12 kV because a brush corona discharge occurs and intense turbulence is generated at the flame front. For both uniform and non-uniform electric fields, the horizontal flame velocity is almost the same.
Mechanical engineering and machinery, Mechanics of engineering. Applied mechanics