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121.
122.
A new kind of polymer composite, produced from the typical polybenzoxazine and 0–30 wt-% native and silane-treated aluminium nitride (T-AlN), was investigated. The mechanical tests revealed a significant increase in the microhardness and flexural properties upon adding the T-AlN particles compared to that obtained from the untreated ones. By adding 0–30 wt-% T-AlN, the tensile moduli were accurately reproduced by the Halpin-Tsai and Nielsen models. At 30 wt-% T-AlN, dynamic mechanical analysis showed a significant increase in the storage moduli and the glass transition temperature (Tg), reaching 3.2?GPa and 217°C, respectively. The thermal stability of these materials was significantly improved upon the addition of the T-AlN fillers. These improvements are attributed to the high thermal and mechanical properties of the fillers and their good dispersion and adhesion in and to the matrix as revealed by a morphological analysis. 相似文献
123.
Jahangiry Hassan A. Gholhaki Majid Naderpour H. Tavakkoli S. Mehdi 《International Journal of Mechanics and Materials in Design》2021,17(4):947-967
International Journal of Mechanics and Materials in Design - This article aims to utilize IsoGeometric analysis (IGA) and Level set method for topology optimization of elastoplastic plane stress... 相似文献
124.
Farshid Nouri-Ahangarani Mehdi Nekoomanesh-Haghighi Milad Karbalaie 《Designed Monomers and Polymers》2016,19(5):394-405
In this article, polymerization of 1-hexene with FeCl3-doped Mg(OET)2/TiCl4/electron donor (ED) catalytic system is presented. For this purpose, first a number of TiCl4 catalysts supported on Mg(OEt)2 and Fe-doped Mg(OEt)2 supports were prepared with ethylbenzoate or dibutylphthalate as the internal EDs. After successive catalysts synthesis, they were employed in 1-hexene polymerization using cyclohexyl methyl dimethoxysilane as external ED as well as without it. The catalysts activity and molecular weight distribution (MWD) of poly 1-hexenes (PHs) were influenced strongly by both FeCl3 doping and donor presence so that a remarkable increase in the catalyst activity was seen in doped catalysts. Deconvolution of MWD curves revealed that increase in the type of active centers by introducing FeCl3 into the support should be responsible for the broadening of MWD of PHs. 13CNMR analysis indicated that while isotacticity does not change considerably by Fe doping, EDs increase its amount as high as 8–21%. Second, the stereoselective behavior of active Ti species in doped and undoped catalysts was fully explored by molecular modeling using density functional theory (DFT) method. Finally, with the aid of rheological measurements, the processability of polymers were evaluated and then the gel permeation chromatography (GPC) results were approved through the values obtained from model fitting as well as changes in moduli crossover modulus. 相似文献
125.
In the modeling of brain mechanics subjected to primary blast waves, there is currently no consensus on how many biological components to be used in the brain–meninges–skull complex, and what type of constitutive models to be adopted. The objective of this study is to determine the role of layered meninges in damping the dynamic response of the brain under primary blast loadings. A composite structures composed of eight solid relevant layers (including the pia, cerebrospinal fluid (CSF), dura maters) with different mechanical properties are constructed to mimic the heterogeneous human head. A hyper-viscoelastic material model is developed to better represent the mechanical response of the brain tissue over a large strain/high frequency range applicable for blast scenarios. The effect of meninges on the brain response is examined. Results show that heterogeneous composite structures of the head have a major influence on the intracranial pressure, maximum shear stress, and maximum principal strain in the brain, which is associated with traumatic brain injuries. The meninges serving as protective layers are revealed by mitigating the dynamic response of the brain. In addition, appreciable changes of the pressure and maximum shear stress are observed on the material interfaces between layers of tissues. This may be attributed to the alternation of shock wave speed caused by the impedance mismatch. 相似文献
126.
The aim of this study was to analyse input–output energy and economical assessment of almond production in three age groups of orchards (group I 6–10, group II 11–15 and group III 16–20 years old) in Chahrmahal-Va-Bakhtiari province, Iran. Data for almond production were collected by administering questionnaire in face-to-face interviews from the orchards selected based on random sampling method during a 3-year period. The results showed that 57,027.13, 60,341.14 and 61,640.43 MJ ha?1 energy was consumed by group I, group II and group III, respectively. The most energy input was consumed by electricity, followed by chemical fertilizer. Energy indices were calculated, and the results revealed that energy efficiency was 0.62, 1.12 and 0.81 in the triple groups of orchards, respectively. Economical assessment showed that total production cost of almond in group I, II and III was $4547.54, $5799.26 and $5687.05 ha?1, respectively. In all orchard groups, the shares of variable and fixed production costs found to be same nearly. Net return for almond production was $14,516.22, $30,735.19 and $21,395.57ha?1, respectively. According to the research results, it was concluded that although almond production in the study region was not an efficient process in terms of energy consumption, it was a profitable agricultural operation. 相似文献
127.
Fatemeh Sadat Sangsefidi Masoud Salavati-Niasari Hossein Khojasteh Mehdi Shabani-Nooshabadi 《International Journal of Hydrogen Energy》2017,42(21):14608-14620
Pure CuO–CeO2 nanocomposites were synthesized by simple thermal decomposition method in presence of various Cu salts as a copper source and fructose as a green capping agent. In this study, the effect of various parameters such as the type of copper sources, temperature and time of reaction on the morphology and the particles size were studied. The products were characterized via X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), N2 adsorption (BET), vibrating sample magnetometer (VSM), and infrared spectrum (FT-IR). The optical property of the nanocomposite was examined via UV–vis (DRS) spectroscopy and the band gap was calculated to 3 eV. Also, the hydrogen storage capacity of CuO–CeO2 nanocomposites and CeO2 nanoparticles were investigated via chronopotentiometry method for the first time. The discharge capacity of CeO2 nanoparticles and CuO–CeO2 nanocomposites in 1 mA current and 20 cycles obtained 2150 and 2450 mAh/g, respectively. 相似文献
128.
This study evaluated the performance of rooftop catchment systems in securing non-potable water supply in Birjand, located in an arid area in southeastern Iran. The rooftop catchment systems at seven study sites of different residential buildings were simulated for dry, normal, and wet water years, using 31-year rainfall records. The trial and error approach and mass diagram method were employed to optimize the volume of reservoirs in five different operation scenarios. Results showed that, during the dry water year from 2000 to 2001, for reservoirs with volumes of 200–20000 L, the proportion of days that could be secured for non-portable water supply was on average computed to be 16.4%–32.6% across all study sites. During the normal water year from 2009 to 2010 and the wet water year from 1995 to 1996, for reservoirs with volumes of 200–20000 L, the proportions were 20.8%–69.6% and 26.8%–80.3%, respectively. Therefore, a rooftop catchment system showed a high potential to meet a significant portion of non-potable water demand in the Birjand climatic region. Reservoir volume optimization using the mass diagram method produced results consistent with those obtained with the trial and error approach, except at sites #1, #2, and #5. At these sites, the trial and error approach performed better than the mass diagram method due to relatively high water consumption. It is concluded that the rooftop catchment system is applicable under the same climatic conditions as the study area, and it can be used as a drought mitigation strategy as well. 相似文献
129.
Seyyed Ahmadreza Amirsadat Babak Moradi Ali Zeinolabedini Hezave Siamak Najimi Mehdi Hojjat Farsangi 《Korean Journal of Chemical Engineering》2017,34(12):3119-3124
Due to the vast production of crude oil and consequent pressure drops through the reservoirs, secondary and tertiary oil recovery processes are highly necessary to recover the trapped oil. Among the different tertiary oil recovery processes, foam injection is one of the most newly proposed methods. In this regard, in the current investigation, foam solution is prepared using formation brine, C19TAB surfactant and air concomitant with nano-silica (SiO2) as foam stabilizer and mobility controller. The measurements revealed that using the surfactant-nano SiO2 foam solution not only leads to formation of stable foam, but also can reduce the interfacial tension mostly considered as an effective parameter for higher oil recovery. Finally, the results demonstrate that there is a good chance of reducing the mobility ratio from 1.12 for formation brine and reservoir oil to 0.845 for foam solution prepared by nanoparticles. 相似文献
130.
In this study, thermal and small-scale effects on the flapwise bending vibrations of a rotating nanoplate, which can be the basis of nano-turbine design, have been analyzed. The nano-turbine is made of an orthotropic nanoplate with a setting angle that is modeled based on the classical plate theory (CPT) with cantilever boundary conditions. The axial forces are also included in the model as the true spatial variation due to the rotation and temperature change. The governing equations and boundary conditions are derived according to Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature method. The effects of small-scale parameter, nondimensional angular velocity, temperature change, and setting angles in the first four nondimensional frequencies are discussed. Due to the consideration of the rotating effects, results of this study are applicable in nano-machines, such as nano-motors, nano-rotor, and other rotating nano-structures. Also, by considering the effect of thermal loading on rotation of a nanoplate, the results are useful in the design of nano-turbines. 相似文献