Hossein Tajmir Riahi  Hamed Amouzegar  Mehrdad Falsafioun 《The Structural Design of Tall and Special Buildings》2015,24(4):300-315

In this paper, seismic collapse of reinforced concrete moment frames is assessed using endurance time (ET) analysis. A set of 30 frames that incorporate deterioration of concrete components is used for this assessment. Application of ET method for collapse assessment of structures is explained, and its accuracy for this purpose is evaluated by comparing its results with incremental dynamic analysis results. Input motions for ET analysis are generated based on ASCE7‐05 design spectrum, and also accelerograms used for incremental dynamic analysis are spectrally matched to the same spectrum. Distribution of different engineering demand parameters over frames height and their values at collapse occurrence are compared for two methods. Results show that spectral accelerations in which collapse occurs in both analyses are very similar for most of the frames, and ET method can appropriately predict the collapse mechanisms of the structures especially for taller frames. Accuracy of ET method in collapse assessment of reinforced concrete moment frames is satisfactory, and this method can be used as a good estimator for study of collapse mechanisms with much less computational effort. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

    

Edris Hoseinzadeh  Mohammad Reza Samarghandi  Farshid Ghorbani Shahna  Ebrahim Chavoshi 《Water and Environment Journal》2013,27(3):418-424

To accomplish this study, the total concentration of suspended particles, PM₁₀ and PM_2.5, was mapped at intercity bus stations in the central square of Hamedan. To measure the particulate matter (PM), portable air sampling systems that collect integrated filter samples were used. The PM concentration was collected at various time intervals and measured gravimetrically. The results were then analysed using the ArcView GIS 3.3 software to map the particulate dispersion patterns. The mean concentrations of the total suspended particles (TSP), PM₁₀ and PM_2.5 were 1220.94 ± 1418.5, 524.7 ± 217.5 and 386 ± 193.6 μg/m³, which were 16, 7.72 and 4.7 times greater than the World Health Organization (WHO) air quality standard, respectively. The PM concentration was not correlated with wind velocity or air temperature, but was correlated with humidity (P = 0.01). Overall, the results of this pilot study indicate that people at bus stations are exposed to respirable particulate matter (RPM) at levels high enough to pose a serious health risk.  相似文献   

    

Hossein Ghalkhani  Saeed Golian  Bahram Saghafian  Ashkan Farokhnia  Asaad Shamseldin 《Water and Environment Journal》2013,27(4):535-548

Developing a robust flood forecasting and warning system (FFWS) is essential in flood‐prone areas. Hydrodynamic models, which are a major part of such systems, usually suffer from computational instabilities and long runtime problems, which are particularly important in real‐time applications. In this study, two artificial intelligence models, namely artificial neural network (ANN) and adaptive neuro‐fuzzy inference system (ANFIS), were used for flood routing in an FFWS in Madarsoo river basin, Iran. For this purpose, different rainfall patterns were transformed to run‐off hydrographs using the Hydrologic Engineering Center (HEC)‐1 hydrological model and routed along the river using HEC river analysis system RAS hydrodynamic model. Then, the simulated hydrographs with different lag times were used as inputs for training of ANN and ANFIS models to simulate flood hydrograph at the basin outlet. Results showed that the simulations obtained from ANN and ANFIS coincided with the results simulated by the HEC‐RAS, and application of such models is strongly suggested as a backup tool for flood routing in FFWSs.  相似文献   

    

Ehssan Nazockdast  Hossein Nazockdast  Fatemeh Goharpey 《Polymer Engineering and Science》2008,48(7):1240-1249

Rheological behavior of polypropylene (PP)/organoclay nanocomposites varying in compatibilizer (PP‐g‐MA) and organoclay concentration was investigated. The samples were prepared by melt intercalation method in an internal mixer. The wide angle X‐ray diffraction patterns and results of rheological measurements showed that the compatibilizer had strong influence in increasing the interlayer spacing. The observed low frequency liquid‐like to solid‐like transition and apparent yield stress in simple shear flows, along with convergence of transient shear stress to nonzero values in stress relaxation after the cessation of flow experiments, were found to be consistent with formation of a physical network in quiescent conditions which could be easily ruptured with applying low shear rates. The values of stress overshoot strain in flow reversal experiments were independent of shear rate, organoclay, and compatibilizer content. From the results of frequency sweep experiments in different nonlinear strain amplitudes it was shown that extended Cox‐Merz analogy was valid in nonlinear dynamic deformations while the shear viscosity showed positive deviation from this analogy with higher deviations at lower shear rates. Results of storage modulus recovery and flow reversal experiments at different shear rates suggested that network structure is reformed with a much slower rate compared to the rotational relaxation of organoclay platelets. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers  相似文献   

    

Hossein Mahdavi  Alireza Badiei  Gholam Hossein Zohuri  Abbas Rezaee  Roghieh Jamjah  Saied Ahmadjo 《应用聚合物科学杂志》2007,103(3):1517-1522

An iron‐based catalyst of 2,6‐bis‐[1‐(2‐methylphenylimino)ethyl]pyridine iron dichloride was prepared. The ligand was prepared using 2,6‐diacetylpyridine as the starting chemical under controlled conditions. The preparation procedure was followed using ¹³C‐NMR, ¹H‐NMR, FT‐IR, MS (mass spectroscopy), and elemental analysis methods. The homogeneous polymerization of ethylene was carried out using the prepared catalyst in toluene media. Methyl aluminoxane (MAO) was used as a cocatalyst. The effect of the [Al] : [Fe] molar ratio, polymerization temperature, and monomer pressure of 202,000 to 454,500 Pa on the polymerization behavior were studied. The highest activity of the catalyst was obtained at 30°C, the activity decreased with increasing temperature, while increasing pressure linearly increased its activity. The molecular weight distribution of the polyethylene obtained was 1.25 to 1.72. A weight average molecular weight of 7.1 × 10⁴ and 1.5 × 10³ were obtained. The crystallinity of the polymer was about 19% and its melting point was about 65°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1517–1522, 2007  相似文献   

    

Jamshid Behin  Syed Salman Bukhari  Vahid Dehnavi  Hossein Kazemian  Sohrab Rohani 《化学工程与技术》2014,37(9):1532-1540

The reuse of industrial wastes from a coal‐fired power plant and a plasma electrolytic oxidation process was attempted to realize a zero discharge. The batch composition was adjusted by adding sodium hydroxide and sodium aluminate. A single‐mode microwave oven equipped with reflux condenser was used for crystallization under atmospheric pressure. The synthesized samples were characterized by X‐ray diffraction, scanning electron microscopy, BET, thermogravimetric analysis, and cation‐exchange capacity (CEC) measurement. Analytical results indicated that Na‐A zeolite with a defined maximum crystallinity could be successfully synthesized by hydrothermal treatment of fly ash with wastewater. Due to the high CEC, the product can be applied for gas purification and soil remediation processes.  相似文献   

    

Fathollah Pourfayaz  Seyed Hassan Jafari  Yadollah Mortazavi  Abbas Ali Khodadadi  Hossein Ali Khonakdar 《Polymer-Plastics Technology and Engineering》2015,54(6):632-638

Different contents of multiwalled carbon nanotube (MWCNTs) functionalized by He-dielectric barrier discharge (DBD) plasma followed by an exposure to NH₃ were incorporated into PA6 matrix via a phase inversion based solution method. Optical and electron microscopic results were indicative of the excellent dispersion state of the MWCNTs. The differential scanning calorimetry and thermogravimetric analysis measurements revealed that even addition of a slight amount of the MWCNTs significantly increased the thermal stability and crystallization temperature. Moreover, the low electrical percolation threshold of the PA 6/functionalized MWCNTs nanocomposites was another confirmation for achieving a good dispersion state of MWCNTs using this approach.  相似文献   

    

Mehdi Entezam  Danial Nozari  Mohammad Mirjalili  Hossein Ali Khonakdar 《Polymer-Plastics Technology and Engineering》2015,54(15):1571-1584

Correlation of rheological response with microstructure and also the tensile mechanical properties of nanoclay-filled polyethylene/ethylene vinyl acetate blends were studied. From transmission electron microscopy observations, the same clay localization within polyethylene- and ethylene vinyl acetate-rich blends was revealed. However, a better clay dispersion in the ethylene vinyl acetate-rich blend was found by analyzing the changes in the linear viscoelastic rheological properties discussed by the fractional Zener model and the power law expression. The clay influences on the tensile properties of polyethylene- and ethylene vinyl acetate-rich blends were in good agreement with its microstructure, implied by the rheological studies.  相似文献   

    

Mohammad Reza Saeb  Hossein Ali Khonakdar  Seyed Hassan Jafari  Hadi Rastin  Udo Wagenknecht  Gert Heinrich 《Polymer-Plastics Technology and Engineering》2015,54(2):223-232

We quantified interfacial adhesion in ternary blends with matrix/shell/core microstructure based on mechanical properties assessments. Various HDPE-based ternary blends containing PA-6/EVOH core/shell droplets were prepared by changing composition and processing temperature. The theoretical predictions of tensile properties were compared with experimental data; thereby considerable shift in experimental modulus from lower to upper limit observed over a 10°C increase in melting temperature. This confirmed the impact of blending temperature on matching the predicted values with experimental data. The meaningful trend observed in tensile characteristics of ternary blends simply gives an understanding of interfacial adhesion degree in ternary blend showing matrix/shell/core microstructure.  相似文献   

    

Mohammad Hossein Keshavarz  Karim Esmailpour  Mehdi Zamani  Akbar Gholami Roknabadi 《Propellants, Explosives, Pyrotechnics》2015,40(6):886-891

The M06‐2X/6‐311G(d,p) and B3LYP/6‐311G(d,p) density functional methods and electrostatic potential analysis were used for calculation of enthalpy of sublimation, crystal density and enthalpy of formation of some thermally stable explosives in the gas and solid phases. These data were used for prediction of their detonation properties including heat of detonation, detonation pressure, detonation velocity, detonation temperature, electric spark sensitivity, impact sensitivity and deflagration temperature using appropriate methods. The range of different properties for these compounds are: crystal density 1.51–2.01 g cm⁻³, enthalpy of sublimation 346.4–424.7 kJ mol⁻¹, the solid phase enthalpy of formation 500.4–860.6 kJ mol⁻¹, heat of detonation 13.64–17.57 kJ g⁻¹, detonation pressure 33.0–37.0 GPa, detonation velocity 8.5–9.5 km s⁻¹, detonation temperature 5488–6234 K, electric spark sensitivity 7.89–9.47 J, impact sensitivity 21–38 J, deflagration temperature 560–586 K and power [%TNT] 207–276. The results show that two novel energetic compounds N,N′‐(diazene‐1,2‐diylbis(2,3,5,6‐tetranitro‐4,1‐phenylene))bis(5‐nitro‐4H‐1,2,4‐triazol‐3‐amine) (DDTNPNT3A) and 1,1′‐(diazene‐1,2‐diylbis(2,3,5,6‐tetranitro‐4,1‐phenylene))bis(3‐nitro‐1H‐1,2,4‐triazol‐5‐amine) (DDTNPNT5A) can be introduced as thermally explosives with high detonation performance.  相似文献