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Enhancing Sound Absorption in Micro-Perforated Panel and Porous Material Composite in Low Frequencies:A Numerical Study Using FEM

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Sound & Vibration 2024年第1期58卷 81-100页

作者： mohammad javad SheikhMozafari Department of Occupational Health Engineering School of Public HealthTehran University of Medical SciencesTehranIran

Mitigating low-frequency noise poses a significant challenge for acoustic engineers,due to their long wavelength,with conventional porous sound absorbers showing limitations in attenuating such *** effective strategy involves combining porous materials with micro-perforated plates(MPP)to address this *** the significant impact of structural variables like panel thickness,hole diameter,and air gap on the acoustic characteristics of MPP,achieving the optimal condition demands numerous sample *** impedance tube’s considerable expense for sound absorption measurement and the substantial cost involved in fabricating each sample using a 3D printer underscore the advantage of utilizing simulation methods to attain the optimal *** study focuses on optimizing low-frequency enhancement by investigating key *** the Finite Element Numerical Method(FEM)in COMSOL software,a composite panel was constructed comprising date palm fiber layers,an intervening air layer,and *** study explored the arrangement of these layers and the impact of parameters like hole diameter,plate thickness,and perforation ratio on acoustic *** selected optimal parameter at each stage was consistently maintained for subsequent *** revealed that layer arrangement significantly influenced acoustic *** the MPP layer before the porous material yielded superior low-frequency *** low-frequency behavior involved reducing hole diameter and perforation ratio while increasing plate *** the porous material’s thickness relative to the air layer behind the MPP enhanced absorption peak and resonance *** conclusion,halving the porous layer’s thickness while incorporating an air layer and single MPP proved more effective than using a thick porous *** approach not only reduces costs and space requirements but also enhances low-frequency *** study highlights the precision of

关键词： Micro-perforated panel date palm natural fibers low and middle frequency noise finite element method

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Stability of Nonlinear Systems Using Optimal Fuzzy Controllers and Its Simulation by Java Programming

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IEEE/CAA Journal of Automatica Sinica 2019年第6期6卷 1519-1527页

作者： mohammad javad Mahmoodabadi Saideh Arabani Mostaghim Department of Mechanical Engineering Sirjan University of TechnologySirjan ***Iran Department of Computer Engineering Faculty of EngineeringUniversity of GuilanRasht 3756Iran

In this paper, at first, the single input rule modules(SIRMs) dynamically connected fuzzy inference model is used to stabilize a double inverted pendulum system. Then, a multiobjective particle swarm optimization(MOPSO) is implemented to optimize the fuzzy controller parameters in order to decrease the distance error of the cart and summation of the angle errors of the pendulums, simultaneously. The feasibility and efficiency of the proposed Pareto front is assessed in comparison with results reported in literature and obtained from other ***, the Java programming with applets is utilized to simulate the stability of the nonlinear system and explain the internetbased control.

关键词： Double inverted pendulum system fuzzy control Java programming multi-objective algorithm particle swarm optimization(PSO)

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Strengthening of reinforced concrete beams using fiberreinforced cementitious matrix systems fabricated with custom-designed mortar and fabrics

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Frontiers of Structural and Civil Engineering 2023年第7期17卷 1100-1116页

作者： Ahmadreza RAMEZANI mohammad Reza ESFAHANI javad SABZI Faculty of Engineering Ferdowsi University of MashhadMashhadIran

The performance of a new fiber-reinforced cementitious matrix(FRCM)system developed using custom-designed mortar and fabrics is investigated in this *** behavior of this system is evaluated in terms of both the flexural and shear strengthening of reinforced concrete *** beams are designed to assess the effectiveness of the FRCM system in terms of flexural strengthening,and four specimens are designed to investigate their shear *** parameters investigated for flexural strengthening are the number of layers,span/depth ratio,and the strengthening *** previous studies,custom fabrics with similar axial stiffness are used in all strengthening methods in this *** the shear-strengthened specimens,the effects of the span/depth ratio and strengthening system type(fiberreinforced polymer(FRP)or FRCM)are *** proposed FRCM system exhibits desirable flexural and shear strengthening for enhancing the load capacity,provides sufficient bonding with the substrate,and prevents premature failure *** the similar axial stiffness of fabrics used in both FRCM and FRP systems and the higher load capacity of specimens strengthened by the former,cement-based mortar performs better than epoxy.

关键词： fiber-reinforced cementitious matrix flexural strengthening shear strengthening carbon fiber-reinforced polymer shear span

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Estimation of photolysis half-lives of dyes in a continuous-flow system with the aid of quantitative structure-property relationship

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Frontiers of Environmental Science & Engineering 2014年第5期8卷 683-692页

作者： Davoud BEIKNEJAD mohammad javad CHAICHI Faculty of Chemistry University of Mazandaran Babolsar 47416-95447 Iron

In this paper the photolysis half-lives of the model dyes in water solutions and under ultraviolet （UV） radiation were determined by using a continuous-flow spectrophotometric method. A quantitative structure- property relationship （QSPR） study was carried out using 21 descriptors based on different chemometric tools including stepwise multiple linear regression （MLR） and partial least squares （PLS） for the prediction of the photolysis half-life （t1/2） of dyes. For the selection of test set compounds, a K-means clustering technique was used to classify the entire data set, so that all clusters were properly represented in both training and test sets. The QSPR results obtained with these models show that in MLR-derived model, photolysis half-lives of dyes depended strongly on energy of the highest occupied molecular orbital （EHoMO）, largest electron density of an atom in the molecule （ED^＋） and lipophilicity （logP）. While in the model derived from PLS, besides aforementioned EHOMO and ED^＋ descriptors, the molecular surface area （Sm）, molecular weight （M-W）, electronegativity （X）, energy of the second highest occupied molecular orbital （EHoMO- 1） and dipole moment （μ） had dominant effects on logt1/2 values of dyes. These were applicable for all classes of studied dyes （including monoazo, disazo, oxazine, sulfo- nephthaleins and derivatives of fluorescein）. The results were also assessed for their consistency with findings from other similar studies.

关键词： dye photolysis half-life quantitative structure-property relationship continuous-flow stepwise multiple linear regression partial least squares

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Relative T-Injective Modules and Relative T-Flat Modules

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Chinese Annals of Mathematics,Series B 2011年第4期32卷 497-506页

作者： mohammad javad NIKMEHR Farzad SHAVEISI Department of Mathematics Faculty of Science K. N. Toosi University of Technology Tehran Iran Department of Mathematics Razi University Kermanshah Iran

Abstract Let T be a Wakamatsu tilting module. A module M is called （n, T）-copure injective （resp. （n, T）-copure flat） if εT^1（N, M） = 0 （resp. Г1^T（N, M） = 0） for any module N with T-injective dimension at most n （see Definition 2.2）. In this paper, it is shown that M is （n, T）-copure injective if and only if M is the kernel of an In（T）-precover f ： A → B with A ∈ ProdT. Also, some results on Prod T-syzygies are presented. For instance, it is shown that every nth Prod T-syzygy of every module, generated by T, is （n, T）-copure injective.

关键词： Wakamatsu tilting module (n T)-Copure injective module (n T)-Copure fiat module T-Projective dimension T-Injective dimension

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Numerical demonstration of three-dimensional terahertz metamaterials based on the causality principle

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Chinese Physics B 2014年第2期23卷 518-523页

作者： Saeid Jamilan javad Nourinia mohammad Naghi Azarmanesh Department of Electrical Engineering Urmia University

A parameter retrieval algorithm based on the causality principle and Kramers-Kronig （KK） relations is employed to calculate the effective parameters of three-dimensional （3D） metamaterials. Using KK relations, the branch selecting problem, which is the challenge of effective parameter retrieval method, can be removed. To reveal the validity of the proposed algorithm, the constitutive refractive index of a homogeneous polymide cube is extracted. The result is in excellent agreement with the intrinsic refractive index of the polymide. Finally, the two terahertz metamaterials with 3D structures are designed and their effective parameters are then retrieved using the proposed algorithm. Numerical simulations are performed using the fuiI-wave electromagnetic solver, CST Microwave Studio.

关键词： metamaterial three-dimensional causality principle Kramers-Kronig relations

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Peak displacement patterns for the performance-based seismic design of steel eccentrically braced frames

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Earthquake Engineering and Engineering Vibration 2019年第2期18卷 379-393页

作者： Ali Fakhraddini Hamed Saffari mohammad javad Fadaee Department of Civil Engineering Shahid Bahonar University of Kerman

Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.

关键词： performance-based seismic design direct displacement-based design displacement pattern eccentrically braced frames steel building

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Application of reliability-centered maintenance for productivity improvement of open pit mining equipment:Case study of Sungun Copper Mine

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Journal of Central South University 2014年第6期21卷 2372-2382页

作者： Amin Moniri Morad mohammad Pourgol-mohammad javad Sattarvand Department of Mining Engineering Sahand University of Technology Department of Mechanical Engineering Sahand University of Technology

Equipment plays an important role in open pit mining industry and its cost competence at efficient operation and maintenance techniques centered on reliability can lead to significant cost *** application of optimal maintenance process was investigated for minimizing the equipment breakdowns and downtimes in Sungun Copper *** results in the improved efficiency and productivity of the equipment and lowered expenses as well as the increased profit *** field operating data of 10 trucks are used to estimate the failure and maintenance profile for each component,and modeling and simulation are accomplished by using reliability block diagram *** analysis was then conducted to select proper probabilistic model for maintenance *** reliability of the system was evaluated and importance of each component was computed by weighted importance measure *** analysis led to identify the items with critical impact on availability of overall equipment in order to prioritize improvement ***,the availability of trucks was evaluated using Monte Carlo simulation and it is revealed that the uptime of the trucks is around 11000 h at 12000 operation ***,uncertainty analysis was performed to account for the uncertainty sources in data and models.

关键词： operating costs maintenance mining dump truck reliability availability uncertainty

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Design and optimization of a nano-antenna hybrid structure for solar energy harvesting application

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Chinese Physics B 2021年第9期30卷 606-617页

作者： mohammad javad Rabienejhad Mahdi Davoudi-Darareh Azardokht Mazaheri Optics and Laser Science and Technology Research Center Malek Ashtar University of TechnologyShahinshahrIran Faculty of Science Department of PhysicsMalek Ashtar University of TechnologyShahinshahrIran Department of Physics University of IsfahanIran

A novel hybrid structure with high responsivity and efficiency is proposed based on an L-shaped frame nano-antenna(LSFNA)array for solar energy harvesting ***,two types of LSFNAs are designed and optimized to enhance the harvesting characteristics of traditional simple electric dipole nano-antenna(SEDNA).The LSFNA geometrical dimensions are optimized to have the best values for the required input impedance at three resonance wavelengths ofλ_(res)=10μm,15μm,and 20μ*** the LSFNAs with three different sizes are modeled like a planar spiral-shaped array(PSSA).Also,a fractal bowtie nano-antenna is connected with the PSSA in the array *** proposed hybrid structure consists of two main elements:(I)Three different sizes of the LSFNAs with two different material types are designed based on the thin-film metal-insulator-metal diodes that are a proper method for infrared energy harvesting.(Ⅱ)The PSSA gap is designed based on the electron field emission proposed by the Fowler-Nordheim theory for the array ***,the proposed device is *** results show that the PSSA not only has an averaged 3-time enhancement in the harvesting characteristics(such as return loss,harvesting efficiency,etc.)than the previously proposed structures but also is a multi-resonance wide-band ***,the proposed antenna takes up less space in the electronic circuit and has an easy implementation process.

关键词： field electron emission infrared metal-insulator-metal(MIM)diode nano-antenna photovoltaic effects rectification solar energy harvesting

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Application of analytical hierarchy process to selection of primary crusher

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International Journal of Mining Science and Technology 2014年第4期24卷 519-523页

作者： Rahimdel mohammad javad Ataei mohammad Faculty of Mining Engineering Sahand University of Technology Faculty of Mining Engineering Petroleum and Geophysics Shahrood University of Technology

Selection of crusher required a great deal of design based on the mining plan and operation input. Selection of the best primary crusher from all of available primary crushers is a Multi-Criterion Decision Making （MCDM） problem, in this paper, the Analytical Hierarchy Process （AHP） method was used to selection of the best primary crusher for Golegohar Iron Mine in Iran. For this reason, gyratory, double toggle jaw, single toggle jaw, high speed roll crusher, low speed sizer, impactor, hammer mill and feeder breaker crushers were considered as alternatives and capacity, feed size, product size, rock compressive strength, abrasion index and mobility of crusher were considered as criteria. As a result of our study, the gyvratory crusher was offered as the best primary crusher for the studied mine.

关键词： MCDMA nalytical Hierarchy Process Primary crusher selection Golegohar Iron Mine

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