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Transactions of Nonferrous Metals Society of China 2024年

作者： Sajad Ghaemifar milad Roostaei Mohammad Reza Zamani Stefan Wurster Hamed Mirzadeh School of Metallurgy and Materials Engineering， College of Engineering， University of Tehran Erich Schmid Institute of Materials Science， Austrian Academy of Sciences Department of Materials Science， Chair of Materials Physics， Montanuniversit?t Leoben

Effects of post-processing heat treatments on the microstructure， aging kinetics， and room/elevated temperature mechanical properties of additively manufactured Inconel 718 superalloy were investigated. Scanning electron microscopy (SEM)， electron backscattered diffraction (EBSD)， and X-ray diffraction (XRD)， as well as hardness， tensile， and creep testing were used for characterization. At temperatures higher than 1100 °C， homogenization treatment resulted in the appearance of equiaxed grains by recrystallization and diminishing the dislocation density. The precipitation activation energy for the homogenized aged condition was obtained as 203 kJ/mol， which was higher than the value of ～160 kJ/mol for the as-built IN718 superalloy. Therefore， direct aging resulted in a faster aging response， which led to a significant improvement in tensile properties， as rationalized by the strengthening mechanisms. Direct aging treatment resulted in a higher elevated-temperature ultimate tensile strength (UTS) as well as the optimum creep life and lowest minimum creep rate in comparison with other heat treating routes， which were attributed to the presence of fine and uniformly dispersed strengthening precipitates in conjunction with the high dislocation density.

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Cardiovascular risk factors affecting COVID-19 outcomes at a tertiary referral hospital in northwest Iran: A prospective cohort study

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Journal of Acute Disease 2024年第1期13卷 8-13页

作者： Mahsa Behnemoon Mojdeh Mehrno Naser Gharebaghi milad Hamdi Department of Cardiology School of MedicineUrmia University of Medical ScienceUrmiaIran Medical Center Urmia University of Medical ScienceUrmiaIran Department of Dermatology and Infectious Disease School of MedicineUrmia University of Medical ScienceUrmiaIran

Objective:To investigate cardiovascular risk factors affecting COVID-19 outcomes in a tertiary referral ***:This prospective cohort study analyzed 269 participants with *** primary outcomes were ICU admission,prolonged hospital stay duration,and in-hospital *** secondary outcomes included death,chronic symptoms,and NYHA functional class during follow-up ***:A total of 412 patients with COVID-19 symptoms were enrolled in the study,and out of which 269 patients had complete medical records and positive SARS-CoV-2 PCR test results,fulfilling the study criteria were *** patients were divided into two groups,with cardiovascular comorbidities(group A,n=122),such as established cardiovascular disease,diabetes mellitus,and hypertension,and without cardiovascular comorbidities(group B,n=147).Binary logistic regression analysis showed that patients with underlying hypertension,diabetes,and established cardiovascular disease had a 1.55(95%CI:1.28-2.26),1.62(95%CI:1.34-2.13),and 1.63(95%CI:1.07-5.34)-fold risk of mortality,respectively in the adjusted ***:Hospitalized COVID-19 patients with predisposing cardiovascular risk factors are more susceptible to develop worse *** attention should be paid to the management and follow-up of these patients.

关键词： COVID-19 Outcome Cardiovascular Chronic symptoms Diabetes mellitus Hypertension

Comparison among the UECM Model, and the Composite Model in Forecasting Malaysian Imports

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Open Journal of Statistics 2024年第2期14卷 163-178页

作者： Mohamed A. H. milad Hanan Moh. B. Duzan Libyan Authority and Science Research Tripoli Libya The Higher Institute of Science and Technology-Souq Algoma Tripoli Libya

For more than a century, forecasting models have been crucial in a variety of fields. Models can offer the most accurate forecasting outcomes if error terms are normally distributed. Finding a good statistical model for time series predicting imports in Malaysia is the main target of this study. The decision made during this study mostly addresses the unrestricted error correction model (UECM), and composite model (Combined regression—ARIMA). The imports of Malaysia from the first quarter of 1991 to the third quarter of 2022 are employed in this study’s quarterly time series data. The forecasting outcomes of the current study demonstrated that the composite model offered more probabilistic data, which improved forecasting the volume of Malaysia’s imports. The composite model, and the UECM model in this study are linear models based on responses to Malaysia’s imports. Future studies might compare the performance of linear and nonlinear models in forecasting.

关键词： Composite Model UECM ARIMA Forecasting Malaysia

Robust Finite-time Synchronization of Non-identical Fractional-order Hyperchaotic Systems and Its Application in Secure Communication

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IEEE/CAA Journal of Automatica Sinica 2019年第1期6卷 228-235页

作者： Hadi Delavari milad Mohadeszadeh the Electrical Engineering Department Hamedan University of Technology

This paper proposes a novel adaptive sliding mode control(SMC) method for synchronization of non-identical fractional-order(FO) chaotic and hyper-chaotic systems. Under the existence of system uncertainties and external disturbances,finite-time synchronization between two FO chaotic and hyperchaotic systems is achieved by introducing a novel adaptive sliding mode controller(ASMC). Here in this paper, a fractional sliding surface is proposed. A stability criterion for FO nonlinear dynamic systems is introduced. Sufficient conditions to guarantee stable synchronization are given in the sense of the Lyapunov stability theorem. To tackle the uncertainties and external disturbances, appropriate adaptation laws are introduced. Particle swarm optimization(PSO) is used for estimating the controller parameters. Finally, finite-time synchronization of the FO chaotic and hyper-chaotic systems is applied to secure communication.

关键词： Adaptive sliding mode control (ASMC) chaos synchronization fractional order (FO) hyper-chaotic system Lyapunov theorem secure communication

Nonlinear vibration analysis of a circular micro-plate in two-sided NEMS/MEMS capacitive system by using harmonic balance method

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Acta Mechanica Sinica 2019年第1期35卷 129-143,I0004页

作者： milad Saadatmand Alireza Shooshtari Department of Electrical Engineering Technical University of DenmarkKgs.LyngbyDenmark Department of Mechanical Engineering Bu-Ali Sina UniversityHamedanIran

In this study, forced nonlinear vibration of a circular micro-plate under two-sided electrostatic, two-sided Casimir and external harmonic forces is investigated analytically. For this purpose, at first, von Karman plate theory including geometrical nonlinearity is used to obtain the deflection of the micro-plate. Galerkin decomposition method is then employed, and nonlinear ordinary differential equations (ODEs) of motion are determined. A harmonic balance method (HBM) is applied to equations and analytical relation for nonlineaT frequency response (F-R) curves are derived for two categories (including and neglecting Casimir force) separately. The analytical results for three cases:(1) semi-linear vibration;(2) weakly nonlinear vibration;(3) highly non linear vibration, are validated by comparing with the numerical solutio ns. After validation, the effects of the voltage and Casimir force on the natural frequency of two-sided capacitor system are investigated. It is shown that by assuming Casimir force in small gap distances, reduction of the natural frequency is considerable. The influences of the applied voltage, damping, micro-plate thickness and Casimir force on the frequency response curves have been presented too. The results of this study can be useful for modeling circular parallel-plates in nano /microelectromechanical transducers such as microphones and pressure sensors.

关键词： Nonlinear vibration Two-sided MEMS capacitor Circular plate Harmonic balance method

Effects of copper content on microstructure and mechanical properties of open-cell steel foams

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International Journal of Minerals,Metallurgy and Materials 2019年第5期26卷 588-596页

作者： Hamid Sazegaran milad Hojati Department of Industrial Engineering Faculty of Engineering Quchan University of Technology Manufacturing Management of Mashhad Powder Metallurgy Company

The effects of copper content on the microstructural and mechanical properties of steel foams are investigated. Spherical urea granules, used as a water-leachable space holder, were coated with a mixture of iron, ultrafine carbon, and different amounts of copper powders. After the mixture was compacted and the space holder was removed by leaching, a sintering process was performed under an atmosphere of thermally dissociated ammonia. Microstructural evaluations of the cell walls were carried out using optical microscopy and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy. In addition, compression tests were conducted to investigate the mechanical properties of the manufactured steel foams. The results showed that the total porosity decreases from 77.2% to 71.9% with increasing copper content in the steel foams. In the foams' microstructure, copper islands are mostly distributed in pearlite and intergranular carbide phases are formed in the grain boundaries. When the copper content was increased from 0 to 4 wt%, the elastic modulus, plateau stress, fracture stress, and fracture strain of manufactured steel foams improved 4.5, 6, 6.4, and 2.5 times, respectively.

关键词： steel foam leachable space holder copper content liquid-phase sintering mechanical properties

Azole derivatives embedded in montmorillonite clay nanocarriers as corrosion inhibitors of mild steel

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International Journal of Minerals,Metallurgy and Materials 2019年第1期26卷 86-97页

作者： milad Edraki Davood Zaarei Polymer Department Technical Faculty South Tehran Branch Islamic Azad University

Azole derivatives such as 2-mercaptobenzothiazole(MBT) and 2-mercaptobenzimidazole(MBI) were introduced as corrosion inhibitors into the interlayer space of sodium montmorillonite clay(Na+-MMT). The corrosion protection behavior of mild steel in solutions containing MBT, MBI, MMT + MBT, MMT + MBI, Na^+-MMT, and NaCl(3.5 wt%) was evaluated using polarization and electrochemical impedance spectroscopy(EIS). Also, the release of penetrated species into the medium from the clay nanocarriers was evaluated using ultraviolet-visible(UV-Vis) spectroscopy. Small-angle X-ray scattering(SAXS) confirmed the insertion of MBT and MBI into the inner space of the clay layers and the interaction between two organic and inorganic phases. Scanning electron microscopy(SEM) was used to assess the morphology of the surface of the steel samples after the samples had been immersed for 24 h in the extraction solution. The corrosion protection in the solutions with clay nanocarriers containing MBT and MBI was better than that in solutions without MMT. The UV-Vis results showed that the release of MBI species from Na+-MMT nanocarriers in neutral pH was far lower than that of MBT species.

关键词： azole derivatives clay minerals release electrochemical impedance spectroscopy corrosion inhibition

Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault or a normal fault: A parametric study

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Frontiers of Structural and Civil Engineering 2020年第4期14卷 998-1011页

作者： Masoud RANJBARNIA milad ZAHERI Daniel DIAS Department of Geotechnical Engineering Faculty of Civil EngineeringUniversity of TabrizTabrizIran Schoo of Automotive and Transportation Engineering Hefei University of TechnologyHefei 230009China Universite Grenoble Alpes Grenoble F-38000France

Urban tunnels crossing faults are always at the risk of severe *** this paper,the efects of a reverse and a normal fault movement on a transversely crossing shallow shotcreted tunnel are investigated by 3D finite difference *** verifying the accuracy of the numerical simulation predictions with the centrifuge physical model results,a parametric study is then *** is,theleffects of various parameters such as the sprayed concrete thickness,the geo-mechanical properties of soil,the tunnel depth,and the fault plane dip angle are studied on the displacements of the ground surface and the tunnel structure,and on the plastic strains of the soil mass around *** results of each case of reverse and normal faulting are independently discussed and then compared with each *** is obtained that deeper tunnels show greater displacements for both types of faulting.

关键词： urban tunnel sprayed concrete reverse fault normal fault finite difference analysis

Influence of glycine additive on corrosion and wear performance of electroplated trivalent chromium coating

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International Journal of Minerals,Metallurgy and Materials 2020年第4期27卷 544-554页

作者： Navid Mehdipour milad Rezaei Zeynab Mahidashti Department of Materials and Metallurgical Engineering Amirkabir University of Technology(Tehran Polytechnic)Hafez Ave.P.O.Box 15875-4413TehranIran

The aim of this study is to evaluate the effect of various molar ratios of glycine to chromium salt(Gly:Cr)and different current densities on the corrosion and wear behaviors of Cr(III)electroplated *** morphology and thickness of the coatings were investigated by scanning electron *** wear properties of the coatings were studied using pin on disk and hardness tests,while corrosion behavior of the coatings was identified using linear polarization,small amplitude cyclic voltammetry,and electrochemical impedance spectroscopy *** increasing the glycine concentration,a structure with low crack density was *** all molar ratios,maximum thickness and current efficiency was observed at a current density of 150 mA·cm?*** the electrochemical methods had a consistent result,and maximum corrosion resistance of approximately 16000Ω·cm2 was obtained in the case of Gly:Cr=3:1 and current density of 200 mA·cm?2.

关键词： electrodeposition trivalent chromium glycine corrosion resistance

Numerical Simulation of Dual-Phase-Lag Model and Inverse Fractional Single-Phase-Lag Problem for the Non-Fourier Heat Conduction in a Straight Fin

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Journal of Thermal Science 2020年第3期29卷 632-646页

作者： MOZAFARIFARD milad AZIMI Aziz MEHRZAD Salem Department of Mechanical Engineering Shahid Chamran University of AhvazAhvaz ***Iran

In recent years,many studies have been done on heat transfer in the fin under unsteady boundary conditions using Fourier and non-Fourier *** this paper,unsteady non-Fourier heat transfer in a straight fin having an internal heat source under periodic temperature at the base was investigated by solving numerically Dual-Phase-Lag and Fractional Single-Phase-Lag *** this way,the governing equations of these models were presented for heat conduction analysis in the fin,and their results of the temperature distribution were validated using the theoretical results of Single and Dual-Phase-Lag *** that,for the first time the order of fractional derivation and heat flux relaxation time of the fractional model were obtained for the straight fin problem under periodic temperature at the base using Levenberg-Marquardt parameter estimation *** solve the inverse fractional heat conduction problem,the numerical results of Dual-Phase-Lag model were used as the *** results obtained from Fractional Single-Phase-Lag model could predict the fin temperature distribution at unsteady boundary condition at the base as well as the Dual-Phase-Lag model could.

关键词： non-Fourier heat transfer fractional calculus inverse heat transfer Levenberg-Marquardt straight fin unsteady boundary condition