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Numerical Study of Aeroacoustic Sound on Performance of Bladeless Fan

Chinese Journal of Mechanical Engineering 2017年第2期30卷 483-494页

作者： mohammad jafari Atta Sojoudi Parinaz Hafezisefat Aerospace Engineering Department Iowa State UniversityAmesUSA Mechanical Engineering Department University of TehranTehranIran Mechanical Engineering Department Iowa State UniversityAmesUSA

Aeroacoustic performance of fans is essential due to their widespread application. Therefore, the original aim of this paper is to evaluate the generated noise owing to different geometric parameters. In current study, effect of five geometric parameters was investigated on well performance of a Bladeless fan. Airflow through this fan was analyzed simulating a Bladeless fan within a 2 m×2 m×4 m room. Analysis of the flow field inside the fan and evaluating its performance were obtained by solving conservations of mass and momentum equations for aerodynamic investigations and FW-H noise equations for aeroacoustic analysis. In order to design Bladeless fan Eppler 473 airfoil profile was used as the cross section of this fan. Five distinct parameters, namely height of cross section of the fan, outlet angle of the flow relative to the fan axis, thickness of airflow outlet slit, hydraulic diameter and aspect ratio for circular and quadratic cross sections were considered. Validating acoustic code results, we compared numerical solution of FW-H noise equations for NACA0012 with experimental results. FW-H model was selected to predict the noise generated by the Bladeless fan as the numerical results indicated a good agreement with experimental ones for NACA0012. To validate 3-D numerical results, the experimental results of a round jet showed good agreement with those simulation data. In order to indicate the effect of each mentioned parameter on the fan performance, SPL and OASPL diagrams were illustrated.

关键词： Bladeless fan · Computational fluid dynamic (CFD) · Aeroacoustic performance · Ffowcs Williams and Hawkings (FW-H) formulation

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Optimal thermal design of anisotropic plates with arbitrary cutouts using genetic algorithm

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Theoretical & Applied Mechanics Letters 2022年第3期12卷 165-177页

作者： mohammad jafari Soheila Yari mohammad jafari Mechanical Engineering Department Shahrood University of TechnologyShahroodIran Faculty of Mechanical and Mechatronics Engineering Shahrood University of TechnologyShahroodIran

Anisotropic plates in different applications may have geometric defects such as openings and *** presence of the opening disturbs the heat flow,which creates significant thermal stress around the *** the heat flux is high enough,these extreme stresses can lead to structural *** article aims to obtain the optimal parameters for achieving the minimum value of the normalized stress near the cutout’s boundary in perforated anisotropic plates utilizing the genetic *** parameters include the curvature of opening’s corners,orientation angle of opening,fibers angle,heat flux angle,and opening’s *** plate is under heat flux,and the opening’s border is thermally *** stress distribution around the opening is calculated using Lekhnitskii’s complex variable method and complex potential *** genetic algorithm is then implemented to find the optimal values for design *** results show that by selecting the optimal parameters related to the anisotropic material and the opening’s geometry,the stress intensity factor of the perforated anisotropic plates is remarkably ***,this optimization algorithm can be extended to find the optimized parameters and achieve the optimal designs in anisotropic and isotropic perforated plates under thermal loadings.

关键词： Anisotropic materials Perforated plate Optimization Genetic algorithm Thermal stress Complex variable method Conformal mapping

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QUASI-PERMUTATION REPRESENTATIONS OF ALTERNATING AND SYMMETRIC GROUPS

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Acta Mathematica Scientia 2007年第2期27卷 297-300页

作者： Houshang Behravesh mohammad Hossein jafari Department of Mathematics University of Urmia UrmiaIran Department of Mathematics University of Tabriz TabrizIran

The quantities c（G）, q（G） and p（G） for finite groups were defined by H. Behravesh. In this article, these quantities for the alternating group An and the symmetric group Sn are calculated. It is shown that c（G... 详细信息

关键词： Quasi-permutation representations alternating groups symmetric groups character theory

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Seismic control of multi-degrees-of-freedom structures by vertical mass isolation method using MR dampers

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 503-510页

作者： Mohamad Shahrokh Abdi Masoud Nekooei mohammad-Ali jafari Department of Civil Engineering Marivan BranchIslamic Azad UniversityMarivan ***Iran Department of Civil Engineering Science and Research BranchIslamic Azad UniversityTehran ***Iran Structural Department of Transmission and Distribution Research Center Niroo Research Institute(NRI)Tehran ***Iran

Vertical mass isolation(VMI)is one of the novel methods for the seismic control of *** this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is located among *** this study,the magnetorheological damper in three modes:passive-off,passive-on,and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two ***-degrees-of-freedom structures with 5,10,and 15 floors in two dimensions were examined under 11 pairs of near field *** each level,the displacement of MR dampers was taken into *** responses of maximum displacement,maximum inter-story drift,and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the *** to the results,the semi-active control method can reduce the response by more than 12%compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the *** method can reduce more than 16%and 20%of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure,respectively.

关键词： seismic control vertical mass isolation base shear magnetorheological damper semi-active control

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Application of perfectly matched layer to soil-foundation interaction analysis

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第4期10卷 753-768页

作者： mohammad Davoodi Abbas Pourdeilami Hosein Jahankhah mohammad Kazem jafari International Institute of Earthquake Engineering and Seismology TehranIran

Despite of the limitation in modeling infinite space, the finite element method(FEM) is one of the most used tools to numerically study the geotechnical problems regarding the capacity of simulating different geometries, conditions and material behaviors. A kind of absorbing layer named perfectly matched layer(PML) has been applied to modeling the radiation damping using FEM, which makes the dynamic analysis of soil-structure interaction more accurate. The PML is capable of absorbing incident waves under any angle and frequency, ensuring them to pass through the model boundaries without *** this context, a new FEM program has been written and the PML formula has been implemented by rewriting the dynamic equation of motion and deriving new properties for the quadrilateral *** analysis of soil-foundation interaction by applying the PML is validated by the evaluation of impedance/compliance functions for different ground conditions. The results obtained from the PML model match the extended mesh results, even though the domain is small enough that other types of absorbing boundaries can reflect waves back to the foundation. The mechanism of the wave propagation in the region shows that the forced vibrations can be fully absorbed and damped by the boundaries surrounded by PMLs which is the role of radiation damping in FEM modeling.

关键词： Perfectly matched layer (PML) Finite element method (FEM) Wave propagation Impedance/compliance

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Woody Species Diversity and Forest Structure from Lowland to Montane Forest in Hyrcanian Forest Ecoregion

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Journal of Mountain Science 2013年第4期10卷 609-620页

作者： Seyed mohammad jafari Shahin ZARRE Seyed Kazem ALAVIPANAH School of Biology and Center of Excellence in Phylogeny of Living Organisms College of Science University of TehranP.O. Box 14155-6455 Tehran Iran School of Biology and Center of Excellence in Phylogeny of Living Organisms College of Science University of TehranTehran Iran Department of Cartography Faculty of Geography University of TehranTehran Iran

Alborz Mountains host Caspian Hyrcanian forest ecoregion along the northern slopes and forest steppe ecoregion in highlands. Hyrcanian forest covers the southeastern part of Caucasus biodiversity hotspot and is of great biogeographic importance. Altitudinal pattern and correlation between woody species biodiversity （DIV）, forest structure （（stem density （DEN）, mean basal area （MBA） and mean height class （MHC）） and disturbance （DIS） were explored along 2,4oo m altitudinal gradient in Hyrcanian relict forest, Central Alborz Mountains. Vegetation changes from lowland forest （LoF） to mid- altitude forest （MiF） and montane forest （MoF） in this area. The altitudinal gradient was divided into twelve 200 m elevational belts. Point centered quarter method （PCQM） with 96 sampling points and 83 vegetation samples by plot method （PM） were used to record field data. Shannon-Wiener index and Pearson coefficient were used for diversity and correlation analysis. The results showed that DEN decreased linearly, MBA and MHC showed relatively hump shaped and DIS showed a reverse hump shaped pattern of change along altitudinal gradient. Woody species diversity decreased non-steadily from LoF to MoF. Transitional vegetations of Carpinus-Fagus and Fagus-Quercus represented higher diversity of woody taxa compared to adjacent homogenous communities. Significant correlation was observed between altitude and all parameters： DEN with MBA, DIS and DIV; MBA with DIS; MHC with DIS along with DIV; and DIS with DIV at the study area scale. Surprisingly,correlation between studied parameters differed within each vegetation type. Altitude probably acts as a proxy for human and environmental driving forces in this area. Stability of warm and wet condition, season length, soil depth along with forest accessibility probably influences the altitudinal pattern of the studied parameters. Disturbance affects forest structure and consequently diversity; especially in lowlands. The obtained results recommend

关键词： Alborz Mountains Biodiversity ForestMensuration Hyrcanian forest Disturbance

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Complexation of Sm^(3+) and pamidronate: A DFT study

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Journal of Rare Earths 2015年第3期33卷 310-319页

作者： Masoud Arabieh mohammad Hassan Khodabandeh mohammad Hossein Karimi-jafari Carlos Platas-Iglesias Karim Zare Computational Chemistry Laboratory NSTRI 11365-8486 Tehran Iran Department of Chemistry Faculty of Science Shahid Beheshti University G.C. Evin 19839-63113 Tehran Iran Department of Bioinformatics Institute of Biochemistry and Biophysics University of Tehran 13145-1384 Tehran Iran Departamento de Química Fundamental Universidade da Coru?a Campus da Zapateira-Rúa da Fraga 10 15008 A Coru?a Spain

We reported a quantum mechanical study of the complexes formed between Sm3＋ and the bisphosphonate ligand pamidronate in aqueous solution. According to available experimental p K a values pamidronate was expected to exist in aqueous solution, at physiologically relevant p H, in its di- and tri-protonated forms（denoted by H3 L and H2L）. The most stable structures of the ligands and Sm3＋ complexes were found by using a detailed analysis of the conformational space with semiempirical and DFT methods. The results showed that both H2 L and H3 L bisphosphonates acted as a tridentate ligands in their complexes with Sm3＋. The addition of explicit water molecules to the coordination sphere of the metal not only gave different coordination numbers for H2 L and H3 L complexes（CN=9 and 10）, but also provided different trends in stabilization energies. The results highlighted the importance of considering not only an explicit first coordination shell, but also a second hydration shell, for an adequate description of this type of complexes in aqueous solution.

关键词： samarium radiopharmaceutical bisphosphonates solvent effects rare earths

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Combined effect of micro silica with clay, and gypsum as mulches on shear strength and wind erosion rate of sands

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International Soil and Water Conservation Research 2019年第4期7卷 388-394页

作者： Fateme Naghizade Asl Hamid Reza Asgari Hojat Emami mohammad jafari Department of Combating Desertification Gorgan University of Agricultural Sciences and Natural Resources***GorganIran Department of Soil Science Ferdowsi University of Mashhad***MashhadIran Department of Combating Desertification Tehran University***TehranIran

Mulching is known as one of the fastest strategies to control wind erosion and sand dunes *** hypothesized that mixed micro silica with clay,gypsum and clay-gypsum as mulches will increase shear strength,threshold friction velocity and decrease soil losses of drifting *** this purpose,mixture of micro silica rates (0,1,5,10,15 and 20%) with clay,gypsum,and clay-gypsum applied on sand *** 60 days of mulching,shear strength,the threshold friction velocity and soil losses at a wind speed of 15 m/S at the height of 20 cm for 20 *** results of this research revealed that the addition of 10% of micro silica in combination with clay and clay-gypsum increased the shear strength up to 10.6 and 37.5% and the threshold friction velocity up to 45.2 and 48.5%,respectively and decreased soil losses up to 100% in comparison with the samples without micro *** micro silica to gypsum had no considerable effect on shear strength,threshold friction velocity and soil *** was concluded that no pozzolanic reaction occurred between micro silica and gypsum and it was found that improvement in mechanical property and erodibility of clay-gypsum mulch was probably due to the pozzolanic reaction between micro silica and *** of 10% of micro silica in combination with clay or clay-gypsum is therefore recommended as suitable mulch.

关键词： Drifting sands Soil loss Threshold friction velocity Micro silica Mulch

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Scleractinian coral communities of Hormuz Island in the PersianGulf

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Acta Oceanologica Sinica 2022年第12期41卷 48-57页

作者： Yamin Pouryousef Jafar Seyfabadi Hamid Rezai Alireza Mahvari mohammad Ali jafari Department of Marine Biology Faculty of Marine SciencesTarbiat Modares UniversityNoor 46417Iran Darya Negar Pars Consulting Engineers Tehran 14669Iran Department of Environment Hormozgan Provincial Directorate Bandar Abbas 79168Iran

The abundance and health of scleractinian coral communities of Hormuz Island were *** this purpose,we employed 20 m line intercept transects—12 in the intertidal zone and 15 subtidally to evaluate coral cover and community *** estimated dead coral coverage was 6.21%±0.81%,while live coral coverage was 16.93%±1.81%,considered as very ***,12 genera were recorded,of which Porites with 11.9%±1.4%live cover was the dominant,while Goniopora had the least cover(0.07%±0.08%).Based on Mann-Whitney U-test,live coral coverage,dead coral coverage,algal coverage,cover of other benthic organisms and abiotic components showed significant univariate differences between zones(p<0.05).The Spearman correlation test between the abundance of biotic and abiotic components indicated significant negative correlation of live coral and sand with zoantharian and significant positive correlation of algae and other benthic organisms with *** reef health indices used for the corals indicated that,in general,the environmental conditions were not suitable,which could be attributed to both natural and anthropogenic factors,the most important of which was zoantharian’overgrowth on the scleractinian corals in this region.

关键词： scleractinian corals zoantharian reef health indices Hormuz Island Persian Gulf

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Cryptocurrencies,gold,and WTI crude oil market efficiency:a dynamic analysis based on the adaptive market hypothesis

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Financial Innovation 2021年第1期7卷 609-634页

作者： Majid Mirzaee Ghazani mohammad Ali jafari Department of Industrial Engineering K.N.Toosi University of TechnologyTehranIran

This study examined the evolving oil market efficiency by applying daily historical data to the three benchmark cryptocurrencies(Bitcoin,Ethereum,and Ripple),gold,and West Texas Intermediate(WTI)crude *** data coverage of daily returns was from August 2015 to April *** applied two alternative tests to examine linear and nonlinear dependency,i.e.,automatic portmanteau and generalized spectral *** analysis of observed results validated the adaptive market hypothesis(AMH)in all markets,but the degree of adaptability between the data was *** this study,we also analyzed the existence of evolutionary behavior in the *** achieve this goal,we checked the results by applying the rolling-window method with three different window lengths(50,100,and 150 days)on the test statistics,which was consistent with the findings of AMH.

关键词： Adaptive market hypothesis Market efficiency Cryptocurrency Evolutionary Rolling windows

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