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Frequency-dependent viscoelasticity effects on the wave attenuation performance of multi-layered periodic foundations

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Applied Mathematics and Mechanics(English Edition) 2024年第3期45卷 407-424页

作者： M.SAFI M.VAKILIFARD M.J.mahmoodi Faculty of Civil Water&Environmental EngineeringShahid Beheshti UniversityTehran ***Iran Faculty of Mechanical and Energy Engineering Shahid Beheshti UniversityTehran ***Iran

In this paper,layered periodic foundations(LPFs)are numerically examined for their responses to longitudinal and transverse modes in the time and frequency *** different unit-cells,i.e.,2-layer,4-layer,and 6-layer unit-cells,comprising concrete/rubber,concrete/rubber/steel/rubber,and concrete/rubber/steel/rubber/lead/rubber materials,respectively,are taken into ***,the viscoelasticity behavior of the rubber is modeled with two factors,i.e.,a frequency-independent(FI)loss factor and a linear frequency-dependent(FD)loss *** the extraction of the complex dispersion curves and the identification of the band gaps(BGs),the simulations of wave transmission in the time and frequency domains are performed using the COMSOL *** parametric studies evaluate the effects of the rubber viscoelasticity models on the dispersion curves and the wave transmission for the longitudinal and transverse *** results show that considering the rubber viscoelasticity enhances the wave attenuation ***,the transverse-mode damping is more sensitive to the viscoelasticity model than its longitudinal *** 6-layer unit-cell LPF exhibits the lowest BG,ranging from 4.8 Hz to 6.5 Hz.

关键词： layered metamaterial periodic foundation complex dispersion curve wave transmission diagram

Nurses'attitude toward patients'safety climate during COVID-19 pandemic:a cross-sectional study

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Frontiers of Nursing 2024年第1期11卷 39-46页

作者： Asra Nassehi Kobra Ghorbanzadeh Somaye Moayedi Javad Jafari Parvin mahmoodi Mojtaba Jafari Department of Nursing Bam University of Medical SciencesBamIran Department of Nursing Khalkhal University of Medical SciencesKhalkhalIran Community Nursing Research Center Department of NursingZahedan University of Medical SciencesZahedanIran Clinical Care Research Center Department of NursingNursing and Midwifery SchoolKurdistan University of Medical SciencesSanandajIran

Objective:Patient safety is a fundamental factor in improving the quality of care provided in ***,it is considered a significant parameter by all healthcare organizations around the *** present study was conducted to investigate the attitude of nurses toward the patient safety climate during the Coronavirus Disease 2019(COVID-19)pandemic in the southeast of ***:This is a cross-sectional descriptive *** all the nurses working in one of the hospitals in the southeast of Iran,171 nurses participated in the study through convenience sampling *** survey was conducted between June 1 and July 30,2020.A 2-part questionnaire including demographic information and an assessment of nurses'attitudes toward patients'safety climate was used for data collection in *** content validity of the scale is(0.77)and reliability was re-calculated and confirmed by the present study with Cronbach's alpha(α=0.9).Data were analyzed by SPSS 20(IBM Corporation,Armonk,New York,United States)using descriptive and analytical statistical ***:The mean score of safety climates was 3.2±5.20(out of 5 scores).The results showed that among all dimensions of the safety climate,only the education dimension was statistically significant between males and females(P<0.001).Also,there was a significant relationship between the overall average of the safety climate and its dimensions according to the people's position only in the dimension of supervisors'attitude(P<0.01)and burnout(P<0.01).Additionally,a significant correlation between the education level and the overall score of safety climate(P<0.01),as well as the supervisor's attitude dimension(P<0.01),was ***:The results showed that the safety climate was at a relatively favorable *** the impact of nurses'attitudes on the safety climate of patients,its improvement seems *** is recommended to design training courses and educate nurses in order to promote a p

关键词： COVID-19 Iran nurses patient safety climate

Optimal motion cueing algorithm for accelerating phase of manned spacecraft in human centrifuge

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Chinese Journal of Aeronautics 2020年第7期33卷 1991-2001页

作者： Ali mahmoodi Isooda KAZEMI Department of Aerospace Engineering Science and Research BranchIslamic Azad UniversityTehran ***Iran

This paper presents a novel optimal Motion Cueing Algorithm(MCA)to control the rotations of a Human Centrifuge(HC)and achieve the best simulation of a Space Craft(SC)*** of the specific forces sensed by astronauts of the SC and the HC have been derived and linearized.A Linear Quadratic Regulator(LQR)controller is implemented for the problem which tends to minimize the error between the two sensed specific forces as well as control input in a cost *** results in control inputs of the HC to generate its sensed specific force as close as possible to the one in the *** algorithm is implemented for both linearized and nonlinear portions of a US space shuttle mission trajectory as a verification using *** longitudinal direction,the proposed MCA,works well when the acceleration is less than 2 g in which the tracking error does not exceed 12%.In lateral direction the tracking is much better even in nonlinear region since the error remains less than 7%for tilting up to 50°.Finally,the effect of weight matrixes in the LQR cost function on overall weight and power of the HC motion system is discussed.

关键词： Accelerating phase Human centrifuge Manned spacecraft Optimal motion cueing Specific force

Energy Gain Investigation in Fast Ignition ICF with Electron Ignition Beam by Changing Fuel Characteristics

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Chinese Physics Letters 2014年第2期31卷 34-36页

作者： Moosavi Mohadeseh Ahmadi masoume Ghasemizad Abbas Department of Physics University of Guilan Rasht Iran

Fast ignition is a method in inertial confinement fusion （ICF） in which an ignition spark in pre-compression fuel is formed by an ultra-intense laser beam. In applying this method, a hot spot is built by relative electrons which are produced by the ultra-intense laser beam. For a better understanding, a fuel energy gain curve based on density is drawn and it can be observed that the ignition by an electron beam has the maximum energy gain. The maximum energy gain has been observed in equimolar DT fuel with a density of 500g/cma and in fuel with tritium （10%） with a density of 1000g/cm^3.

关键词： INERTIAL confinement fusion NUCLEAR fuels LASER beams ELECTRON beams NUCLEAR energy ENERGY density

Kerosene-alumina nanofluid flow and heat transfer for cooling application

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Journal of Central South University 2016年第4期23卷 983-990页

作者： M.mahmoodi Sh.Kandelousi Department of Aerospace Engineering Malek-Ashtar University of Technology Department of Mechanical Engineering Babol University of Technology

Kerosene-alumina nanofluid flow and heat transfer in the presence of magnetic field are studied. The basic partial differential equations are reduced to ordinary differential equations which are solved semi analytically using differential transformation method. Velocity and temperature profiles as well as the skin friction coefficient and the Nusselt number are determined analytically. The influence of pertinent parameters such as magnetic parameter, nanofluid volume fraction, viscosity parameter and Eckert number on the flow and heat transfer characteristics is discussed. Results indicate that skin friction coefficient decreases with increase of magnetic parameter, nanofluid volume fraction and viscosity parameter. Nusselt number increases with increase of magnetic parameter and nanofluid volume fraction while it decreases with increase of Eckert number and viscosity parameter.

关键词： magnetic field nanofluid heat transfer differential transformation method

Walk-off reduction,using an external optical plate and Bessel-Gaussian interaction

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Chinese Physics B 2015年第2期24卷 215-222页

作者： masoume Mansouri Mohsen Askarbioki Saeed Ghavami Sabouri Alireza Khorsandi Department of Physics University of Isfahan

To reduce the walk-off angle of the extraordinary third-harmonic ultraviolet wave at 355 nm generated by type ⅡKTiOPO4 and type I β-BaB2O4 optical crystals,and the Gaussian output beam of a Q-switched Nd：YAG laser,a simple theoretical model was developed based on a rotatable BK7 plate of variable *** rotating the plate up to 35°along the beam direction,we reduced the walk-off angle up to ~ 13%.The same phenomenon is predicted by the model,confirming the performance of the *** is found that,due to the walk-off effect,the intensity profile of the thirdharmonic generation beam is slightly *** compensate for the observed phenomena and further reduce the walkoff,we used a combination of a convex lens and an axicon to transform the beam profile of the interacting fundamental and second-harmonic generation waves to the zero-order Bessel-Gaussian *** a result,the walk-off is decreased to~ 48.81 mrad,providing ~ 30%relative *** using the same BK7 plate rotated up to 35° along the third-harmonic beam direction,the walk-off angle is further reduced to 38.9 ***,it is observed that the beam profile of the emerged Bessel-Gaussian third-harmonic generation beam remains unchanged with no degradation.

关键词： Bessel-Gaussian beam walk-off third-harmonic generation

HEAT-RESISTANT PYRIDINE-BASED POLY(ETHER-ESTER)S: SYNTHESIS, CHARACTERIZATION AND PROPERTIES

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Chinese Journal of Polymer Science 2013年第1期31卷 171-178页

作者： Shahram Mehdipour-Ataei Ali mahmoodi Department of Chemistry Islamic Azad University

A pyridine-based diacid was synthesized via nucleophilic substitution reaction of 4-hydroxy benzoic acid with 2,6- dichloropyridine in the presence of potassium carbonate. The diacid was characterized using FT-IR and 1H-NMR spectroscopic methods and also with elemental analysis. Polycondensation reaction of the diacid with different diols including 1,4-dihydroxy benzene, 1,5-dihydroxy naphthalene, bis-phenol A and bis-phenol-P resulted in preparation of pyridine-based poly（ether-ester）s. The polymers were characterized and their physical and thermal properties including inherent viscosity, molecular weight, solubility, thermal stability, thermal behavior and crystallinity were studied. They revealed high heat-resistance and improved solubility in polar solvents. Structure-property relations for the prepared polyester were also studied.

关键词： Polyester Polymer synthesis and characterization Thermal properties Structure-property relations.

An optimal energy management development for various configuration of plug-in and hybrid electric vehicle

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Journal of Central South University 2015年第5期22卷 1737-1747页

作者： Morteza Montazeri-Gh Mehdi mahmoodi-K Systems Simulation and Control Laboratory School of Mechanical EngineeringIran University of Science and Technology Tehran P.O.Box 16846-13114 Iran

Due to soaring fuel prices and environmental concerns, hybrid electric vehicle(HEV) technology attracts more attentions in last decade. Energy management system, configuration of HEV and traffic conditions are the main factors which affect HEV's fuel consumption, emission and performance. Therefore, optimal management of the energy components is a key element for the success of a HEV. An optimal energy management system is developed for HEV based on genetic algorithm. Then, different powertrain system component combinations effects are investigated in various driving cycles. HEV simulation results are compared for default rule-based, fuzzy and GA-fuzzy controllers by using ADVISOR. The results indicate the effectiveness of proposed optimal controller over real world driving cycles. Also, an optimal powertrain configuration to improve fuel consumption and emission efficiency is proposed for each driving condition. Finally, the effects of batteries in initial state of charge and hybridization factor are investigated on HEV performance to evaluate fuel consumption and emissions. Fuel consumption average reduction of about 14% is obtained for optimal configuration data in contrast to default configuration. Also results indicate that proposed controller has reduced emission of about 10% in various traffic conditions.

关键词： plug-in and hybrid electric vehicle energy management configuration genetic fuzzy controller fuel consumption emission

Nonlinear integral resonant controller for vibration reduction in nonlinear systems

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Acta Mechanica Sinica 2016年第5期32卷 925-934页

作者： Ehsan Omidi S.Nima mahmoodi Nonlinear Intelligent Structures Laboratory Department of Mechanical Engineering The University of Alabama

A new nonlinear integral resonant controller（NIRC） is introduced in this paper to suppress vibration in nonlinear oscillatory smart structures. The NIRC consists of a first-order resonant integrator that provides additional damping in a closed-loop system response to reduce highamplitude nonlinear vibration around the fundamental resonance frequency. The method of multiple scales is used to obtain an approximate solution for the closed-loop *** closed-loop system stability is investigated using the resulting modulation equation. Finally, the effects of different control system parameters are illustrated and an approximate solution response is verified via numerical simulation *** advantages and disadvantages of the proposed controller are presented and extensively discussed in the results. The controlled system via the NIRC shows no high-amplitude peaks in the neighboring frequencies of the resonant mode,unlike conventional second-order compensation *** makes the NIRC controlled system robust to excitation frequency variations.

关键词： Active vibration control Cantilever Highamplitude oscillation Method of multiple scales Nonlinear vibration Piezoelectric actuator Smart structure