Variation Of Parameters Research Articles

Implications of using simplified finite element meshes to identify material parameters of articular cartilage

The objective of this work was to determine the effects of using simplified finite element (FE) mesh geometry in the process of performing reverse iterative fitting to estimate cartilage material parameters from in situ indentation testing. Six bovine tibial osteochondral explants were indented with sequential 5 % step-strains followed by a 600 s hold while relaxation force was measured. Three sets of porous viscohyperelastic material parameters were estimated for each specimen using reverse iterative fitting of the indentation test with (1) 2D axisymmetric, (2) 3D idealized, and (3) 3D specimen-specific FE meshes. Variable material parameters were identified using the three different meshes, and there were no systematic differences, correlation to basic geometric features, nor distinct patterns of variation based on the type of mesh used. Implementing the three material parameter sets in a separate 3D FE model of 40 % compressive strain produced differences in von Mises stresses and pore pressures up to 25 % and 50 %, respectively. Accurate material parameters are crucial in any FE model, and parameter differences influenced by idealized assumptions in initial material property determination have the potential to alter subsequent FE models in unpredictable ways and hinder the interpretation of their results.

Sustainable high-speed milling enhancement of GnP-reinforced titanium nanocomposites under dry environment

No studies have been done on using graphene nanostructure reinforcement material to improve titanium alloy's dry high-speed machining performance, which is crucial for green manufacturing. This study seeks to understand the impact of graphene on improving the high-speed machining of Ti6Al4V (Ti64) nanocomposites. High-density Ti64-based nanocomposite samples with varying amounts of GnPs (0 wt%, 0.6 wt%, 1.2 wt%, and 2.4 wt%) were fabricated using ball milling and HFIHS sustainable technologies. Subsequently, a detailed investigation was conducted to examine the impact of the GnP contents on high-speed milling performance, namely, cutting force components, surface quality, and machined surface and subsurface microhardness. The variable milling parameters include the cutting speed and feed rate. The results showed that the inclusion of GnPs significantly affected the dry high-speed milling of the nanocomposites. The nanocomposites containing 1.2 wt% and 2.4 wt% of GnP-Ti64 exhibited lower cutting forces than the base-Ti64 without GnP (0 wt% Gnp). At a 100 m/min cutting speed, the cutting and feed forces decreased by 35% and 44%, respectively, compared to the base-Ti64 specimens. This is attributed to lower machining friction due to the presence of graphene and TiC (formed due to the reaction of Ti and GnP particles during sintering) at grain boundaries, facilitating material removal and reducing cutting force. Although the nanocomposites had a higher microhardness, they all showed improved surface quality in comparison to the base-Ti64 specimens. For example, at a feed rate of 270 mm/min the nanocomposites contain 0.6 wt%, 1.2 wt%, and 2.4 wt.% GnPs showed roughness reductions of 6%, 27%, and 38%, respectively, compared to the base-Ti64. Regarding surface and sub-surface hardness after machining, the 2.4 wt.% GnP samples showed superior performance in terms of minimal post-milling hardness variations compared to the base hardness of the material. All GnP-Ti64 milled specimens showed considerably improved surface morphology compared to the base-Ti64 machined specimens. Overall, the nanocomposites containing 1.2 wt% and 2.4 wt% GnPs are strong contenders for reducing cutting forces, enhancing surface roughness, and lowering the fluctuations in microhardness, leading to green manufacturing.

Determining the effect of additional tank volume and air pressure in the spring on the dynamic indicators of a pneumatic system of spring suspension in high-speed railroad rolling stock

The object of this study is the pneumatic system in the spring suspension of rolling stock under conditions of high-speed movement from 170 to 250 km/h. Based on the thermodynamic model of the pneumatic spring suspension system, the influence of volume of the additional tank and the initial pressure in the pneumatic spring on the nature of change in the spring's dynamic stiffness, energy losses, and damping coefficient was studied. Based on the built "force-deformation" dependences for the pneumatic spring, it was established that the change in the volume of an additional tank has a slight effect on the deformation of the pneumatic spring at different speeds of the high-speed rolling stock. It was established that in the range of rolling stock speeds of 170–250 km/h, the diameter of the connecting pipeline is 30 mm, and the volume of the additional tank is from 30 to 60 l, the maximum change in the dynamic stiffness of the pneumatic spring up to 15.5 % occurs at the pressure in the spring of 6.5 bar. Dependences of energy loss and damping coefficient during the operating cycle of the pneumatic spring suspension system were derived. It was established that an increase in the volume of the additional tank and the initial pressure in the pneumatic spring leads to an increase in the energy loss during the operation cycle of the pneumatic system. The maximum values of the damping coefficient over the entire considered range of variable parameters are 1.16–1.29. It was established that with the volume of the additional tank in the range from 30 to 50 liters, the maximum values of the damping coefficient are observed at a diameter of the connecting pipeline of 25 mm and a speed of movement from 200 to 250 km/h. And with an additional tank volume of 60 liters – with a diameter of 30 mm and a speed of 170 to 250 km/h

Detection and Localization of Spine Disorders from Plain Radiography.

Spine disorders can cause severe functional limitations, including back pain, decreased pulmonary function, and increased mortality risk. Plain radiography is the first-line imaging modality to diagnose suspected spine disorders. Nevertheless, radiographical appearance is not always sufficient due to highly variable patient and imaging parameters, which can lead to misdiagnosis or delayed diagnosis. Employing an accurate automated detection model can alleviate the workload of clinical experts, thereby reducing human errors, facilitating earlier detection, and improving diagnostic accuracy. To this end, deep learning-based computer-aided diagnosis (CAD) tools have significantly outperformed the accuracy of traditional CAD software. Motivated by these observations, we proposed a deep learning-based approach for end-to-end detection and localization of spine disorders from plain radiographs. In doing so, we took the first steps in employing state-of-the-art transformer networks to differentiate images of multiple spine disorders from healthy counterparts and localize the identified disorders, focusing on vertebral compression fractures (VCF) and spondylolisthesis due to their high prevalence and potential severity. The VCF dataset comprised 337 images, with VCFs collected from 138 subjects and 624 normal images collected from 337 subjects. The spondylolisthesis dataset comprised 413 images, with spondylolisthesis collected from 336 subjects and 782 normal images collected from 413 subjects. Transformer-based models exhibited 0.97 Area Under the Receiver Operating Characteristic Curve (AUC) in VCF detection and 0.95 AUC in spondylolisthesis detection. Further, transformers demonstrated significant performance improvements against existing end-to-end approaches by 4-14% AUC (p-values < 10-13) for VCF detection and by 14-20% AUC (p-values < 10-9) for spondylolisthesis detection.

Late time acceleration in Bianchi type-V dark energy cosmological models with linear deceleration parameter

We present a Bianchi type-V cosmological model with deceleration parameter as a simple linear function of the Hubble parameter interacting with a perfect fluid in the general theory of relativity. For Bianchi type-V space-time, the available solutions of Einstein field equations have been procure under the assumption of linear deceleration parameter, q = A + BH, where H is the Hubble parameter. Also,during the evolution of the Bianchi-V universe, dark energy(DE) with a variable EoS parameters has been studied in detail and w slowly varies around w = –0.33 for a 10 GYr. lapse, which involves an accelerated expansion, through an expansion not compatible with current. In this article, we discuss the physical and geometrical facets of the cosmological parameter of the model. Several elements of the model universe are explained by the jerk parameter and energy conditions, including the recent cosmological expansion and singularity theories. We also deliberated state-finder parameters, which forecast that the Universe created from Einstein’s static era rallies towards ΛCDM model (r = 1, s = 0).

Shear resistance test analysis and calculation method of shear capacity of UHPC-NC beam without web reinforcement

In order to study the failure phenomenon and shear resistance performance of UHPC-NC beams without web reinforcement, shear resistance tests were carried out on 15 UHPC-NC beams without web reinforcement. The variation parameters were shear span ratio, web thickness, steel fiber content, and compressive stress level. The load-deflection curve, failure phenomenon and crack development of the test beam are analyzed. The test results show that the joint between the top plate and the bottom plate of UHPC-NC I-beam without web reinforcement is the weakest, and the cracked web is easy to be “cut off” at the joint; The “banding crack area” of web is closely related to the shear span ratio, and the width of ribbon area increases with the increase of shear span ratio. The shear capacity of UHPC-NC I-beam without web reinforcement decreases with the increase of shear-span ratio. The shear capacity increases with the increase of web thickness and compressive stress level. The shear capacity has little relationship with steel fiber content, and the initial stiffness of the structure can be improved by applying prestress. Finally, considering the influence of the top slab compression-shear zone and the bottom slab tension-shear zone on the shear capacity of UHPC-NC prestressed composite beams without web reinforcement, the corresponding calculation method of shear capacity is given based on the modified compression field theory and the idea of sub-item superposition, and the applicability of the calculation method is verified by the test results.

Exploring the boiling point elevation of multicomponent salt solution by changing vapor pressure and solution composition

This paper applies thermodynamics theory to analyze the main factors that affect the boiling point elevation (BPE) of salt solutions. By using the vapor pressure measurement method, boiling point experiments were conducted on several common inorganic salts used in industrial wastewater treatment and desalination at different concentrations and temperatures. The experimental data shows that the BPE of a salt solution is approximately a quadratic function of the solution temperature at constant concentration, and the BPE of tri-ion salt solutions tends to be higher than that of NaCl solution at the same concentration. Based on theoretical analysis and a summary of experimental results, it was found that BPE is not only related to solute concentration but also to the number of ionized solute ions. It was also found that replacing the compound concentration with the ion concentration as the independent variable of concentration can reduce the impact of electrolyte ionization and reduce variable parameters. Furthermore, the impact of ion types on BPE was studied in mixed salt solutions. The results show that the higher the average ion activity coefficient of the solute, the higher the boiling point of the solution. Through nonlinear fitting analysis of experimental data, a correlation for calculating the BPE of multi-component salt solutions in industrial water treatment is proposed based on solution temperature and ion concentration.

Electrochemical impedance spectroscopy of AB3 active electrode in nickel metal hydride accumulators: The effect of temperatures and immersion times

The electrochemical impedance spectroscopy (EIS) method was employed systematically to investigate the kinetic properties of the LaY2Ni9 electrode, which serves as negative electrode in Ni-MH accumulators. Through this analysis, a comprehensive understanding of the electrode’s behaviour was achieved.EIS measurements were performed on the LaY2Ni9 electrode at different temperatures (ranging from 15 °C to 75 °C) and at different immersion times using a potentiostat and frequency response analyser.The EIS spectra were fitted using an equivalent circuit model to extract the electrode impedance parameters, such as the charge transfer resistance, Rtc, the absorption/double layer capacities, Cad and Cdl, the specific current density, I0,EIS, and the hydrogen penetration depth, δ. The results show that temperatures have significant effects on the EIS impedance of the LaY2Ni9 electrode. The Rtc and the Cdl parameters increase with temperature, indicating a decrease in electrode kinetics due to the higher activation energy and an increase in electrode area due to thermal expansion. The penetration depth, δ, is directly proportional to the temperature increase.According to the EIS results, it is generally considered advantageous to maintain an operating temperature of around 30 °C for the LaY2Ni9 electrode. Moreover, a correlation can be observed between the variations in the kinetic parameter (DH) and the corresponding changes in other electrochemical parameters.Inconsistencies arise when comparing the exchange current density values obtained through cyclic voltammetry (I0,CV) and impedance spectroscopy (I0,EIS), highlighting contradictory findings. These disparities can be ascribed to multiple factors, including temperature variations, electrode geometry, and concentration gradients near the electrode interface. Overall, this study provides valuable information on the performance and degradation mechanisms of the LaY2Ni9 electrode under temperature and immersion time conditions and highlights the importance of EIS impedance measurements for battery research and development.

Entropy optimized radiative flow conveying hybrid nanomaterials [formula omitted] with melting heat characteristics and Cattaneo-Christov theory: OHAM analysis

Here flow for radiative hybrid-nanomaterial (MgO+MoS2) satisfying Darcy-Forchheimer relation is addressed. Ethylene glycol C2H6O2 is utilized as a base fluid. Magnesium oxide (MgO) and Molybdenum disulfide (MoS2) are considered as distinct nanoparticles. Thermal expression is examined through heat generation and viscous dissipation. Analysis for Cattaneo-Christov theory is carried out. Condition for melting heat is deliberated. Entropy generation is examined. Variable thermal conductivity of hybrid nanomaterial is taken. Suitable transformations are implemented to obtain nonlinear dimensionless systems. Optimal homotopy analysis method (OHAM) is implemented for computations. Temperature, velocity and entropy generation are scrutinized physically. Nusselt number and skin friction are discussed. Conclusion synthesis salient points. Present work is relevant in metallurgical engineering and polymer processing. The findings conclude that Forchheimer number correspond to decline in velocity. Entropy rate and thermal field have similar trend for heat generation variable. A decrease in velocity against melting variable is noted. Temperature increases for variable thermal conductivity and thermal relaxation parameters. Entropy optimization improved for Brinkman number. Skin friction decays for porosity parameter and Forchheimer number. Skin friction improves for melting variable and Forchheimer number. Entropy augments against higher thermal relaxation time. Higher melting variable lead to an enhancement for Nusselt number. There is an improvement for radiation through Nusselt number and temperature.

Variations in the Solar Modulation Parameter Over the Last 9.5 Thousand Years and the Tilt of the Geomagnetic Dipole

Background: Calculations of the solar modulation parameter (Φ) over the past millennia typically use the relationship between the production rate of cosmogenic isotopes, the earth's dipole moment, and the magnitude of Φ. The cosmogenic isotopes 14C and 10Be are typically used in these studies. When studying solar modulation, the cyclic change in dipole tilt is usually not taken into account, which affects estimates of past solar activity. Methods: Tree rings are a reliable basis for obtaining a radiocarbon time scale (IntCal13). However, determining the concentration of 14C in tree rings is a difficult and controversial task. The time scale derived from the 10Be production rate simulation (GICC05) is less reliable. Nevertheless, there is a way to combine the accuracy of the radiocarbon time scale with the reliability of estimates of the 10Be production rate. This method is the synchronization of the radiocarbon and beryllium-10 series. We have selected the most relevant methods for calculating the solar modulation parameter Φ for the Holocene. When calculating Φ, 10Be data synchronized with 14C data were used. The latest data on the earth's dipole moment were considered. Empirical Mode Decomposition (EMD) was used in the analysis of Φ. Results: It has been shown that the first two decomposition modes are oscillating components with periods of 710 and 208 years, the amplitudes of which increase with time, reaching a maximum of 2500 BP. From contemplation, it follows that the 710-year oscillations are apparently caused by fluctuations in the tilt of the earth's dipole. After excluding the EMD component associated with the 710-year cyclicity, a corrected series was obtained for the solar modulation parameter, free from the influence of changes in the tilt of the magnetic dipole. Conclusion: The rate of formation of cosmogenic radionuclides depends on the intensity of penetration of Galactic Cosmic Rays (GCRs) into the earth's atmosphere. Before reaching earth, GCRs must cross the heliosphere, where they are exposed to solar modulation. Adequate consideration of solar modulation parameters is important for the correct interpretation of the rate of production of cosmogenic isotopes and solar activity.

A microwave-regenerable multi-walled carbon nanotube/polyaniline/Fe3O4 ternary nanocomposite for quantifiable sorption of cationic and anionic dyes

The coexistence of toxic dyestuffs in the aquatic environment requires the urgent development of a multifunctional sorbent for their efficient sequestration from aqueous solutions. To achieve this objective, a ternary nanocomposite consisting of an amphoteric, multi-walled, carbon nanotube/polyaniline/magnetite (MWCNTs/PANI/Fe3O4) was successfully synthesized through the co-precipitation of magnetite (Fe3O4) onto the surface of a pre-existing binary composite of MWCNTs/PANI. The structural and morphological features of MWCNTs/PANI/Fe3O4 were scanned using a variety of analysis methods: Fourier transform infrared spectroscopy; both scanning and transmission electron microscopies; energy-dispersive X-ray analysis; thermogravimetric analysis. The capacity of MWCNTs/PANI/Fe3O4 to adsorb cationic dye (Methylene blue, MB), and anionic dye (Congo red, CR) were discerned inclusively under variable operational parameters. The sorption processes of both MB and CR dyes onto MWCNTs/PANI/Fe3O4 were pH-dependent. The sorption process of both dyes onto MWCNTs/PANI/Fe3O4 was reported to fit with the Langmuir model, while the sorption kinetics fitted with the pseudo-second-order kinetic model. The prepared MWCNTs/PANI/Fe3O4 exhibited satisfactory sorption capacities of 142.85 mg g−1 (initial solution pH (pH0): 2.94) and 166.66 mg g−1 (pH0 = 10.03) of the CR and MB dyes, respectively. Dye adsorption followed the monolayer chemisorption phenomenon. The sorption process was exothermic. The application of microwave irradiation caused effective regeneration, and this finding confirmed the renewability of the composite for at least 4 successive sorption/desorption cycles. Using MWCNTs/PANI/Fe3O4 ternary nanocomposite in dye removal looks promising, as its high adsorption capacity, magnetic properties, and renewability offer an efficient, sustainable, and easily recoverable solution for removing dyes from wastewater.

Stacking regression model approach to mixed convection flow of ternary- nanofluid over slanted surface with magnetic field, waste discharge concentration, and joule heating effects

The current work is carried out to investigate the mixed convection flow behavior of ternary-based nanofluid over an inclined surface in the presence of a magnetic field, waste discharge concentration, and joule heating effects. The governing equations with proper assumptions were converted into ordinary differential equations (ODEs) form by implementing suitable similarity constraints and solved with Runge Kutta Fehlberg 4th 5th order and shooting scheme. The stacking regression model approach is implemented along with the Runge Kutta Fehlberg 4th 5th order technique. The obtained outcomes are presented with graphs, and model correctness is assessed using the combination of Gaussian Process Regression (GPR), Extra Tree Regression (ETR), and Random Forest (RF). The consistency and stability of the model are demonstrated by the closely linked testing and training data. The study outcomes show that the rise in the magnetic constraint will improve the velocity profile while improved values of local pollutant external source and external pollutant source variation parameters will enhance the concentration profile. Enhancement in Eckart number and solid volume fraction values will improve the rate of thermal distribution. Ternary nanofluid shows significant improvement than nanofluid. The surface drag force is increased about 8 %-9 % in assisting flow case and 8 %-17 % for opposing flow case for different values of magnetic parameter, the rate of thermal distribution improved from 75.54 % to 11.55 % in assisting flow case and 16.87 % to 25.70 % in opposing flow case for different values of Eckert number. The study's results might contribute to the advancement of more effective heat exchangers and cooling systems for electronics and engines. Exploration and extraction of oil, as well as the creation of efficient water purification systems.

Axial compressive performance and finite element analysis on spirally reinforced seawater sea-sand concrete-filled aluminum alloy tube columns

Axial compression experiment and finite element analysis were used in this research to explain the mechanical properties of spirally reinforced seawater sea-sand concrete-filled aluminum alloy tube (SR-CFAT) columns. The diameter and spacing of the spiral stirrup, the quantity and diameter of the longitudinal reinforcement, and the ratio of the spiral stirrup to longitudinal reinforcement (rhv) were used as the variation parameters in the design of 16 SR-CFAT columns and 1 seawater sea-sand concrete-filled aluminum alloy tube (CFAT) column. The results demonstrated that both the SR-CFAT columns and the CFAT column experience shear failure, while the former exhibited greater axial compression bearing capacity and deformation capacity. The ultimate bearing capacity, ductility, and energy absorption value of this composite column increase with an increase in rhv, then decrease under the same reinforcement content. The specimens perform best under axial compression when rhv is 2.20. Among the others, specimens with "fine and dense" spiral stirrups and "less and coarse" longitudinal reinforcement have higher ultimate bearing capacities, ductility, and energy absorption values. An FE model is created for the SR-CFAT columns, followed by a parameter extension analysis. Based on test and finite element results, a high-accuracy axial compression bearing capacity calculation algorithm is provided using cylinder theory.

Adaptive synergetic control for electronic throttle valve system

AbstractThis study has developed adaptive synergetic control (ASC) algorithm to control the angular position of moving plate in the electronic throttle valve (ETV) system. This control approach is inspired by synergetic control theory. The adaptive controller has addressed the problem of variation in systems parameters. The control design includes two elements: the control law and adaptive law. The adaptive law is developed based on Lyupunov stability analysis of the controlled system, and it is responsible for estimating the potential uncertainties in the system. The effectiveness of the proposed adaptive synergetic control has been verified by numerical simulation using MATLAB/Simulink. The results showed that the ASC algorithm could give good tracking performance in the presence of uncertainty perturbations. In addition, a comparison study has been made to compare the tracking performance of ASC and that based on conventional synergetic control (CSC) for the ETV system. The simulated results showed that the performance of ASC outperforms that based on CSC. Moreover, the results showed that the estimation errors between the actual and estimated uncertainties are bounded and there is no drift in the developed adaptive law of ASC.

Investigation of long-term degradation of the interface in the anchorage zone of GFRP-RC beams

In the long-term service process of Glass Fiber Reinforced Polymer – Reinforced Concrete (GFRP-RC) structures, degradation of GFRP bars and concrete materials can occur, leading to a partial loss of the internal bonding performance of the structure. In this paper, a long-term study on the interface performance of GFRP-RC beams was conducted over an 8-year period to investigate the long-term degradation characteristics of the interface materials and the long-term Effective Anchorage Length (EAL) of GFRP bars. Firstly, a comprehensive analysis from a review perspective was conducted on the long-term degradation mechanisms of concrete and GFRP bars that considers the chemical behavior between microscopic molecules, the two-dimensional (2D) structure observed through micro electron microscopy, and the three-dimensional (3D) structure revealed by micro-X-ray imaging. Secondly, a new EAL calculation model is derived, and the long-term variation parameters of EAL under different conditions are determined. It was observed that the influence of alkaline corrosion and sustained loading is relatively small compared to the influence of initial structural defects on EAL. Finally, a comparison with four international standards revealed that the anchorage length design provided by JSCE-97 and ACI 440–1R-15 is overly conservative for GFRP bars, with values approximately 2–3 times the test results. On the other hand, CSA-S806–12 and CSA S6–19 standards are relatively close to the test values. Considering both design rationality and long-term corrosion resistance, it is concluded that the CSA-S806–12 specification is more reasonable.

Operation optimization of cement clinker production line based on neural network and genetic algorithm

The operation control plays a great role in the running performance of an industrial process. To achieve a successful control, the key point is searching for the target value of the control parameters. The relationship between operation parameters and performance parameters is usually nonlinear and complex, so it is hard to control an industrial process excellently with workers' experience. Based on a large amount of actual operation data, a bridge between control parameters and performance parameters might be built by the neural network. Prediction model is established by using neural network, genetic algorithm was then used to refine these parameters, the optimal condition can be further achieved by combining the relation bridge and genetic algorithm (GA). Paying attention to a cement clinker production process, this article established an optimizing approach based on the neural network and genetic algorithm and one-year operation data (615 sets). The feeding mass rate of raw meal and coal at the precalciner and the feeding coal mass rate at the rotary kiln are selected as the main independent variable and control parameters, and the specific standard coal consumption is determined as the key performance parameter and the optimization objective function. The mean square error and the correlation coefficient of the established neural network model are 12.84 and 0.89, respectively. The relative errors of approximately all prediction data (92.52 %) are within ±5 %. The optimal values for the raw meal feeding rate, the coal feeding rate into precalciner, and the coal feeding rate into rotary kiln are 259.57 t/h, 7.84 t/h, and 7.40 t/h, respectively. In that optimal condition, the specific standard coal consumption reaches 80.00 kgstandard coal/tclinker (This is a relative value, as there is a slight drift in zero point of the factory's instruments). A highly accurate neural network model is developed, which can significantly reduce standard coal consumption and improve industrial energy efficiency.

Dynamic Analysis of Functionally Graded Sandwich Doubly Curved Nanoshells Using Variable Nonlocal Elasticity Theory

Sandwich nanoshells consisting of functionally graded materials (FGMs) offer promise in aerospace, energy and biomedical applications due to their tunable properties. However, a comprehensive understanding of the vibration behavior of such shells is lacking. This work develops an efficient analytical model to study free vibration of sandwich nanoshells with three FGM configurations: FGM face-sheets and metal core (Type A), FGM face-sheets and ceramic core (Type B), and FGM core and face-sheets (Type C). A doubly curved shell geometry representing spherical, hyperbolic–parabolic and cylindrical shells in addition to flat plates is considered. Effective material properties of nanolaminates are computed using a volume fraction-based model. First-order shear deformation theory and modified nonlocal elasticity theory with variable nonlocal parameters are employed to derive the governing equations. Hamilton’s principle is used to obtain the equations of motion. Navier’s solution technique analytically solves the equations for simply supported boundary conditions. Accuracy is validated through comparisons with literature results. Parametric studies analyze the influence of thickness ratio, material gradation, nonlocal parameter, and shell type on frequencies. Results show that Type A configuration yields the highest frequencies. Dimensionless frequency decreases with increasing nonlocal parameter and side-to-thickness ratio. The model provides design insights into vibration behavior of such nanosandwich structures with potential applications in nanodevices and energy harvesting.

Research on the ignition mechanism and structural optimization of turbulent jet pre-chamber in GDI engines

Turbulent jet ignition has been widely studied, but it is mainly focused on gas engines, the igniting mechanisms of pre-chamber (PC) on GDI engines and the contributions of heat and radicals of the jet in inhomogeneous charge still remain to be clarified. Thus, 3-D simulations with comprehensive spray mixing process were performed under variable structural parameters. The decoupling results of thermal and chemical effects show that the influence of jet temperature on the heat release rate (HRR) inside main chamber (MC) is greater than that of free radicals. The mechanism of hot jet ignition containing free radicals in MC is flame propagation without ignition delay. However, compared to jet temperature, the free radicals in the jet have less effects on HRR in MC after the ignition. The nozzle diameter significantly affects fuel entry into the PC, influencing the pressure difference between PC and MC, and thus the jet velocity and duration. The optimal diameter in this study is 1.0 mm, and the jet duration is prolonged for too small or too large diameters. The nozzle angle is constrained by combustion chamber geometry, with the optimal angle being 140° to avoid jet impingement on cylinder head or piston.

Mechanical properties of steel fiber reinforced recycled concrete under compression-shear stress state

The continuous urbanization of construction has led to an increasing demand for concrete, resulting in large-scale gravel and river sand mining, which seriously affect the sustainable development of the environment. The waste concrete produced by the demolition of old buildings is processed into recycled aggregate to replace natural aggregate, and then the preparation of recycled concrete can effectively alleviate this problem. This paper investigates the mechanical properties of steel fiber reinforced recycled concrete (SFRRAC) under compression shear conditions, a compression shear test with 99 cubic specimens was designed, with the variation parameters being recycled aggregate concrete replacement rate, compressive stress, and steel fiber content. The failure mode of SFRRAC under compression-shear stress was observed, and the shear force-displacement curve was calculated. Furthermore, a thorough examination was performed to assess the mechanical characteristics of SFRRAC specimens under compression-shear stress. The findings of this study suggest that as the compressive stress increases, the failure characteristics of the specimens shift from exhibiting brittle failure to displaying ductile failure. The shear strength is most sensitive to the change in compressive stress. When the compressive stress reaches 6 MPa, the shear strength can reach 3.41 times that of the direct shear specimen. The shear strength of SFRRAC specimens is composed of the bond strength of concrete, shear expansion strength, and friction shear strength. The incorporation of steel fibers can modify the distribution of shear strength among the individual components. The adverse effect of the recycled aggregate replacement rate on the toughness index of the specimen is mainly concentrated after the peak point. Nevertheless, an elevation in compressive stress and the inclusion of steel fibers can counterbalance this detrimental influence. The shear strength calculation formula of SFRRAC in shear state is put forward, which has a reference value. This study provides an experimental reference and a theoretical basis for further examination of SFRRAC.

Study the variation of current density & corrosion behavior of modified M2 tool steel: Simulation & experimental

In this study, the simulation of the current density was carried out through COMSOL Multiphysics on surface-modified M2 high-speed tool steel. The results demonstrated that in the presence of the nitride layer on the surface of M2, the current density was increased remarkably in the nitride layer and M2 was immune, and consequently, it can be predicted that the corrosion resistance was increased. For verification, the surface modification through plasma nitriding was applied on the M2 steel corrosion resistance and was evaluated through polarization and electrochemical impedance spectroscopy (EIS) in the 3.5 wt% of NaCl solution. The results confirmed the simulation outcomes; therefore, optimization of the parameters was performed. The impression of the variation of the process parameter of plasma nitriding such as temperature (500, 550, and 600 °C), time (4, 6, and 8 h), and ratio of inserted gases (N2/H2: 1:3, 1:1, 3:1) on the growth of the diffusive layer was assessed by X-Ray Diffractometry (XRD). Outcomes illustrated that applying plasma nitriding causes the formation of the different nitride phases on the top surfaces of the M2 substrate and Fe3N is the dominant phase. The diffusive nitride layer has a higher current density based on simulation results. The microhardness of the surface increased remarkably and 2414 HV was reached as a maximum surface hardness. By considering the obtained results, 500 °C, 6 h, and a ratio of 1:1 of N2/H2 were chosen as optimum conditions of the plasma nitriding of M2 high-speed tool steel, and a corrosion rate of 1.62 mpy was calculated.