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Approximation of structural damping and input excitation force

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Frontiers of Structural and Civil Engineering 2017年第2期11卷 244-254页

作者： mohammad salavati Institute of Structural Mechanics Faculty of Civil Engineering Bauhaus University Weimar Weimar 99423 Germany

Structural dynamic characteristics are the most significant parameters that play a decisive role in structural damage assessment. The more sensitive parameter to the damage is the damping behavior of the structure. The complexity of structural damping mechanisms has made this parameter to be one of the ongoing research topics. Despite all the difficulties in the modeling of damping, there are some approaches like as linear and nonlinear models which are described as the energy dissipation throughout viscous, material or structural hysteretic and frictional damping mechanisms. In the presence of a mathematical model of the damping mechanisms, it is possible to estimate the damping ratio from the theoretical comparison of the damped and un-damped systems. On the other hand, solving the inverse problem of the input force estimation and its distribution to each SDOFs, from the measured structural responses plays an important role in structural identification process. In this paper model-based damping approximation method and a modelless structural input estimation are considered. The effectiveness of proposed methods has been carded out through analytical and numerical simulation of the lumped mass system and the results are compared with reference data. Consequently, high convergence of the comparison results illustrates the satisfactory of proposed approximation methods.

关键词： structural modal parameters damping identification method input excitation force identification Inverse problem

Mechanical responses of pristine and defective hexagonal boron-nitride nanosheets:A molecular dynamics investigation

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Frontiers of Structural and Civil Engineering 2020年第3期14卷 623-631页

作者： mohammad salavati Arvin MOJAHEDIN Ali Hossein Nezhad SHIRAZI Institute of Structural Mechanics Bauhaus-Universitat WeimarWeimar D-99423Germany

ABSTRACT In this work we conducted classical molecular dynamics(MD)simulation to investigate the mechanical characteristics and failure mechanism of hexagonal boron-nitride(h-BN)*** and defective structure of h-BN nanosheets were considered under the uniaxial tensile loadings at various *** defective structure contains three types of the most common initial defects in engineering materials that are known as cracks,notches(with various length/size),and point vacancy defects(with a wide range of concentration).MD simulation results demonstrate a high load-bearing capacity of extremely defective(amorphized)h-BN *** results also reveal that the tensile strength decline by increasing the defect content and temperature as *** MD results provide a comprehensive and useful vision concerning the mechanical properties ofh-BN nanosheets with/without defects,which is very critical for the designing of nanodevices exploiting the exceptional physics of h-BN.

关键词： hexagonal boron-nitride mechanical properties crack notch point defects molecular dynamics

A deep energy method for functionally graded porous beams

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2021年第6期22卷 492-498页

作者： Arvin MOJAHEDIN mohammad salavati Timon RABCZUK Institute of Structural Mechanics Bauhaus-Universitat WeimarWeimar 99423Germany Institute of Material Science and Technology Department of Materials EngineeringTechnische Universitat BerlinBerlin 10623Germany Division of Computational Mechanics Ton Due Thang UniversityHo Chi Minh CityVietnam Faculty of Civil Engineering Ton Due Thang UniversityHo Chi Minh CityVietnam

We present a deep energy method(DEM)to solve functionally graded porous *** use the EulerBernoulli assumptions with varying mechanical properties across the *** is subsequently developed,and its performance is demonstrated by comparing the analytical solution,which was adopted from our previous *** proposed method completely eliminates the need of a discretization technique,such as the finite element method,and optimizes the potential energy of the beam to train the neural *** the neural network has been trained,the solution is obtained in a very short amount of time.

关键词： Energy-based method Multilayer perceptron methodology Functionally graded porous materials Euler-Bernoulli beam theory

Influence of ZrB2 Nanoparticles on the Mechanical and Thermal Behaviors of Carbon Nanotube Reinforced Resol Composite

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Journal of Materials Science & Technology 2016年第7期32卷 611-616页

作者： Zahra Amirsardari Rouhollah Mehdinavaz-Aghdam Masoud salavati-Niasari mohammad Reza Jahannama Institute of Nano Science and Nano Technology University of Kashan. Kashan. Iran Department of Nanotechnology. Space Transportation Research Institute Iranian Space Research Center Tehran lran

The present study focuses on the thermal response of carbon fiber-reinforced phenolic composites, where the matrix has been modified with different reinforcements. Two types of materials, multiwalled carbon nanotubes and zirconium diboride （ZrB2）, were used in a new design of mixture to produce the heat- resistant ablative composite system. The CNT/ZrB2/carbon/phenolic nanocomposite （Z/NT-CR） system corresponding to CNT/carbon/phenolic nanocomposite （NT-CR） showed a reasonable decrease in mass loss and the ablation rate as compared to carbon/phenolic composite （CR）. However, substantial drop in two factors was found for Z/NT-CR as compared to carbon/phenolic and NT-CR. Ablation mechanisms for all three composites were investigated by thermal gravimetric analysis in conjunction with micro- structural studies using a field emission scanning electron microscope. The microstructural studies revealed that CNTs acted as an ablation resistant phase for protection against 2000 ℃, and the conversion from ZrB2 to ZrO2 played an important role as an insulator in the performance of char layer in the ablation resistance.

关键词： Multiwalled carbon nanotubes (MWCNTs)Zirconium diboride nanoparticles (ZrB2)Carbon/phenolic compositeThermal stabilityAblation performance

Risk factors for congenital nasolacrimal duct obstruction in children under two years of age

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国际眼科杂志 2025年第1期25卷 17-23页

作者： Rozhin Kasiri Gholamreza Khataminia Ali Kasiri mohammad Sadegh Mirdehghan mohammad Armin Kasiri Infectious Ophthalmologic Research Center Ahvaz Jundishapur University of Medical SciencesAhvaz ***Iran Islamic Azad University Tehran Medical Sciences Tehran ***Iran

·AIM:To identify various risk factors that may play a significant role in the development of congenital nasolacrimal duct obstruction(CNLDO).·METHODS:This observational case-control study included a case group of 122 children less than two years of age with CNLDO who underwent probing and irrigation treatment at the ophthalmology department of Imam Khomeini Hospital in Ahvaz,Iran,from June 2022 to June2024.A control group of 122 age-matched children without CNLDO was also included for *** was collected from the children's medical records.·RESULTS:The study found a significant correlation between the occurrence of CNLDO and several maternal factors,such as preeclampsia,the use of levothyroxine,hypothyroidism,having more than three pregnancies(gravidity>3),natural pregnancy,and gestational diabetes ***,in children,factors,such as oxygen therapy,anemia,reflux,jaundice,and a family history of CNLDO in first-degree relatives were associated with CNLDO,and maternal preeclampsia and hypothyroidism were found to significantly increase the risk of developing CNLDO in children.·CONCLUSION:Given that CNLDO affects both premature and full-term children,the present findings may potentially facilitate the early identification of children and infants at risk of nasolacrimal duct obstruction,thereby preventing the onset of chronic dacryocystitis.

关键词： risk factors congenital nasolacrimal duct obstruction children

Quantitative Analysis of Holmium Ion by a Ho^3＋ Ion-Selective Sensor Based on a Symmetric Thio-Schiff＇s Base

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Chinese Journal of Chemistry 2011年第7期29卷 1523-1528页

作者： Hassan, Ali Zamani Fatemeh, Rahimi Fatemeh, Naghavi-Reyabbi Ali, Arvinfar Alihossien, Imani mohammad, Reza Ganjali Farnoush, Faridbod Masoud, salavati-Niasari Department of Applied Chemistry Quchan Branch Islamic Azad University Quchan Iran Resident of General Surgery Endoscopic & Minimaly Invasive Surgery Research Center Ghaem Hospital Faculty of Medicine Mashhad University of Medical Sciences Mashhad Iran Center of Excellence in Electrochemistry Faculty of Chemistry University of Tehran Tehran lran Department of Chemistry Faculty of Science University of Kashan Kashan Iran

A poly（vinyl chloride）（PVC） membrane sensor for holmium ions was fabricated based on N-[（Z）-l-（2-thienyl）- methylidene]-N-[4-（4-{[（Z）-l-（2-thienyl）methylidene]amino} phenoxy）phenyl] amine （TPA） as a new ion carrier, acetophenon （AP） as plasticizing solvent mediator and sodium tetraphenyl borate （NaTPB） as an anion excluder. The electrode shows a good selectivity towards Ho^3＋ ions respect to other inorganic cations, including alkali, alka- line earth, transition and heavy metal ions. The constructed sensor displays a Nernstian behavior （19.5±0.3 mV/decade） over the concentration range of 1.0× 10^-6 to 1.0 ×10^- 2 mol·L^-1 with the detection limit of the electrode being 4.6）〈 10-7 mol·L^-1 and very short response time （ca. 5 s）. It has a useful working pH range of 3.2-9.8 for at least 8 weeks. The electrode was successfully applied as an indicator electrode for the potentiometric titration of a Ho^3＋ solution with EDTA and holmium determination in some alloys. The proposed sensor accuracy was studied by the determination of Ho^3＋ in mixtures of three different ions.

关键词： holmium ion PVC membrane sensor potentiometry Schiffs base ion-selective electrode

Decoding molecular mechanisms:brain aging and Alzheimer's disease

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Neural Regeneration Research 2025年第8期20卷 2279-2299页

作者： Mahnoor Hayat Rafay Ali Syed Hammad Qaiser mohammad Uzair Khalid Al-Regaiey Roaa Khallaf Lubna Abdullah Mohammed Albassam Imdad Kaleem Xueyi Wang Ran Wang Mehwish SBhatti Shahid Bashir Atta-ur-Rahman School of Applied Biosciences(ASAB) National University of Sciences and Technology(NUST)IslamabadPakistan Department of Biotechnology Quaid-i-Azam UniversityIslamabadPakistan Department of Biological Sciences Faculty of Basic&Applied SciencesInternational Islamic University Islamabad(IIUI)IslamabadPakistan Department of Bioengineering King Fahd University of Petroleum and MineralsDhahranSaudi Arabia Department of Physiology College of MedicineKing Saud UniversityRiyadhSaudi Arabia Department of Neurology Neuroscience CenterKing Fahad Specialist HospitalDammamSaudi Arabia Department of Mental Health Neuroscience CenterKing Fahad Specialist HospitalDammamSaudi Arabia Department of Biosciences Commission on Science and Technology for Sustainable Development in the South(COMSATS University)IslamabadPakistan Department of Psychiatry The First Hospital of Hebei Medical UniversityShijiazhuangHebei ProvinceChina Mental Health Institute of Hebei Medical University ShijiazhuangHebei ProvinceChina Department of Neurobiology and Behavior University of CaliforniaIrvineCAUSA Neuroscience Center King Fahad Specialist Hospital DammamDammamSaudi Arabia

The complex morphological,anatomical,physiological,and chemical mechanisms within the aging brain have been the hot topic of research for *** aging process alters the brain structure that affects functions and cognitions,but the worsening of such processes contributes to the pathogenesis of neurodegenerative disorders,such as Alzheimer's *** these observable,mild morphological shifts,significant functional modifications in neurotransmission and neuronal activity critically influence the aging *** these changes is important for maintaining cognitive health,especially given the increasing prevalence of age-related conditions that affect *** review aims to explore the age-induced changes in brain plasticity and molecular processes,differentiating normal aging from the pathogenesis of Alzheimer's disease,thereby providing insights into predicting the risk of dementia,particularly Alzheimer's disease.

关键词： Alzheimer’s disease brain aging cognitive health dementia molecular mechanisms neuronal activity neuroplasticity neurotransmission

Resilience-oriented intentional islanding of reconfigurable distribution power systems

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Journal of Modern Power Systems and Clean Energy 2019年第4期7卷 741-752页

作者： mohammad Hossein OBOUDI mohammad mohammadI mohammad RASTEGAR Department of Power and Control Engineering School of Electrical and Computer EngineeringShiraz UniversityShirazIran

The participation of distributed energy resources in the load restoration procedure,known as intentional islanding,can significantly improve the distribution system *** system reconfiguration can effectively alter islanding procedure and thus provide an opportunity to supply more demanded energy and reduce distribution system *** addition,high-impact events such as hurricanes and earthquakes may complicate the procedure of load restoration,due to the disconnection of the distribution system from the upstream grid or concurrent component *** paper presents a two-level method for intentional islanding of a reconfigurable distribution system,considering high-impact *** thefirst level,optimal islands are selected according to the graph model of the distribution *** the second level,an optimal power flow(OPF)problem is solved to meet the operation constraints of the islands by reactive power control and demand side *** proposed problem in the first level is solved by a combination of depth first search and particle swarm optimization *** OPF problem in the second level is solved in DIgSILENT *** proposed method is implemented in the IEEE 69-bus test system,and the results show the validity and effectiveness of the proposed algorithm.

关键词： Intentional islanding Active distribution system Distributed energy resource Distribution system reconfiguration Distribution system resilience

Global Practical Stabilization of Discrete-Time Switched Affine Systems via a General Quadratic Lyapunov Function and a Decentralized Ellipsoid

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IEEE/CAA Journal of Automatica Sinica 2021年第11期8卷 1837-1851页

作者： mohammad Hejri Department of Electrical Engineering Sahand University of TechnologySahand New TownTabriz 51335-1996Iran

This paper addresses the problem of global practical stabilization of discrete-time switched affine systems via statedependent switching *** attempts have been made to solve this problem via different types of a common quadratic Lyapunov function and an *** classical results require either the quadratic Lyapunov function or the employed ellipsoid to be of the centralized *** some cases,the ellipsoids are defined dependently as the level sets of a decentralized Lyapunov *** this paper,we extend the existing results by the simultaneous use of a general decentralized Lyapunov function and a decentralized ellipsoid parameterized *** proposed conditions provide less conservative results than existing works in the sense of the ultimate invariant set of attraction *** different approaches are proposed to extract the ultimate invariant set of attraction with a minimum size,i.e.,a purely numerical method and a numerical-analytical *** the former,both invariant and attractiveness conditions are imposed to extract the final set of matrix *** latter is established on a principle that the attractiveness of a set implies its ***,the stability conditions are derived based on only the attractiveness property as a set of matrix inequalities with a smaller *** examples are presented to prove the satisfactory operation of the proposed stabilization methods.

关键词： Decentralized quadratic Lyapunov function decentralized ellipsoid discrete-time switched affine systems practical stabilization switching power converters