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排序方式: 共有219条查询结果,搜索用时 31 毫秒
31.
Mojtaba Baghban S. Hossein Mansouri Zohreh Shams 《Journal of Mechanical Science and Technology》2014,28(2):739-745
The solution of an inverse, conduction-radiation problem in a two-dimensional rectangle is analyzed to determine the temperature-dependent emissivity at the boundary. The medium is gray, absorbing, emitting and isotropically scattering. The bounding surfaces are assumed to be opaque and diffuse. The inverse problem is solved by minimizing the performance function, which is expressed by the sum of square residuals between estimated and exact heat fluxes, using a combined method of genetic algorithm and conjugate gradient. The emissivity is assumed to be represented as a function of boundary temperature with unknown variables. Therefore, the inverse problem is treated by the estimation of these variables. Finally, four examples are presented to show the accuracy of the algorithm. The effect of the measurement errors on the accuracy of the inverse analysis is also investigated. Results show the algorithm can estimate the unknown emissivity when the measurement errors are neglected. Also it is found that increasing the measurement error decreases the accuracy of estimation of temperature-dependent emissivity. 相似文献
32.
Hesabi ZR Allam NK Dahmen K Garmestani H A El-Sayed M 《ACS applied materials & interfaces》2011,3(4):952-955
In the present study, we report for the first time synthesis of TiO(2) nanotubes/CNTs heterojunction membrane. Chemical vapor deposition (CVD) of CNTs at 650 °C in a mixture of H(2)/He atmosphere led to in situ detachment of the anodically fabricated TiO(2) nanotube layers from the Ti substrate underneath. Morphological and structural evolution of TiO(2) nanotubes after CNTs deposition were investigated by field- emission scanning electron microscopy (FESEM), glancing angle X-ray diffraction (GAXRD), and X-ray photoelectron spectroscopy (XPS) analyses. 相似文献
33.
A nitrate-selective electrode based on surfactant-modified zeolite (SMZ) particles into carbon paste was proposed (SMZ-CPE). The electrode was fully characterized in terms of composition, response time, ionic strength, thermal stability and usable pH range. The electrode containing 10% SMZ exhibited linear response range to nitrate species in the range of 1.00 × 10−6 to 1.00 × 10−3 M with a detection limit of 1.00 × 10−6 M and a Nernstian slope of 59.4 ± 0.7 mV per decade of nitrate concentration. The response of the electrode to nitrate remains constant in the pH ranges of 3.5–9.8 and 1.7–10.5 for 1.00 × 10−4 and 1.00 × 10−2 M nitrate, respectively, and in presence of 1 × 10−4 to 1 × 10−3 M NaCl. The response of the electrode reaches to its equilibrium value within several seconds (10 s) after immersing the electrode in nitrate solution. Selectivity coefficients showed multivalent anions (such as arsenate, dichromate and sulfate) have higher interferences than monovalent anions (such as iodide, fluoride, bromide, chloride and thiocyanate). The electrode was used for determination of nitrate in an ammonium nitrate fertilizer sample, using direct potentiometry, and the satisfactory results were obtained. The electrode was also used for the potentiometric titration of nitrate. The validation of the obtained results in each case was proved by statistical “t” and “g” tests. 相似文献
34.
Zohreh Taghvaee Zahra Piravivanak Karamatollah Rezaei Mohammad Faraji 《Food Analytical Methods》2016,9(5):1220-1227
The cleanup method of modified low temperature was compared with the standardized method of modified ultrasound-assisted liquid–liquid (UALL) extraction for the analysis of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil and refined pomace olive oil. The modified UALL extraction consisted in purification on C18 reversed-phase, Florisil-bonded-phase and NH2 cartridges, and modified low-temperature extraction was followed by alumina-N and NH2 solid-phase extraction (SPE) cartridges. Both methods are followed by reversed-phase high-performance liquid chromatography with fluorescence detection. The chromatograms of the final extracts showed lower interferences in both of the methods. The solvent consumption and cost for the modified UALL method were higher than those of the modified low temperature, and also, it needed more equipment, but its analysis time was less. The limit of detection and limit of quantitation of the modified UALL method were 0.16–0.97 and 0.57–2.93 μg kg?1, respectively, and for the modified low temperature, they were 0.09–1.97 and 0.29–5.99 μg kg?1, respectively. The PAH recoveries for the modified UALL extraction method ranged from 75.0 to 111.0 % (RSD?=?3–8 %), and for the modified low temperature, they ranged from 81.5 to 113.8 % (RSD?=?3–10 %). 相似文献
35.
Low-velocity impact tests are performed on fiberglass/AZ31B-H24 magnesium fiber-metal laminates (FMLs) with various configurations in order to gain a better understanding of the effect of an impactor's features on the response of this type of FML. For that, impactors with two different shapes (hemispherical and sharp-edged) and sizes are used to impact the specimens. The impact response data, such as the deformation of the contact location and energy absorption, is obtained directly during the impact tests through the impact equipment, while mechanical sectioning was carried out to establish the extent of delaminated area and post-impact residual deformation. While the sharp-edged impactor caused the development of cracks on the metal constituent, and delamination within the specimens, the hemispherical ones imposed more influence over the residual deformation. Noticeable differences are observed in response of FML specimens made with two and three layers of magnesium, especially with respect to the energy absorption capacity. Moreover, finite-element analysis, as a major part of this study, has been employed to simulate the low-velocity impact response of FML specimens. The behavior of specimens has been simulated using the commercial finite-element code ABAQUS. The results imply that there is a good agreement between the experimental and numerical results. 相似文献
36.
The shear stress distribution in circular channels was modeled in this study using gene expression programming (GEP). 173 sets of reliable data were collected under four flow conditions for use in the training and testing stages. The effect of input variables on GEP modeling was studied and 15 different GEP models with individual, binary, ternary, and quaternary input combinations were investigated. The sensitivity analysis results demonstrate that dimensionless parameter y/P, where y is the transverse coordinate, and P is the wetted perimeter, is the most influential parameter with regard to the shear stress distribution in circular channels. GEP model 10, with the parameter y/P and Reynolds number (Re) as inputs, outperformed the other GEP models, with a coefficient of determination of 0.7814 for the testing data set. An equation was derived from the best GEP model and its results were compared with an artificial neural network (ANN) model and an equation based on the Shannon entropy proposed by other researchers. The GEP model, with an average RMSE of 0.0301, exhibits superior performance over the Shannon entropy-based equation, with an average RMSE of 0.1049, and the ANN model, with an average RMSE of 0.2815 for all flow depths. 相似文献
37.
Journal of Computational Electronics - Synaptic plasticity is studied herein using a voltage-driven memristor model. The bidirectional weight update technique is demonstrated, and significant... 相似文献
38.
Zohreh Shaghaghi Mehri Aligholivand Rahim Mohammad-Rezaei 《International Journal of Hydrogen Energy》2021,46(1):389-402
Synthesis of stable catalysts for water splitting is important for the renewable and clean energy production. Here, water oxidation activities of cobalt (II) complexes CoL1-CoL3 (1–3) with salophen type ligands (N,N′-bis(salicylidene)-4-chloro-1,2-phenylendiamine (H2L1), N,N′-bis(salicylidene)-4-bromo-1,2-phenylendiamine (H2L2) and N,N′-bis(salicylidene)-4-nitro-1,2-phenylendiamine (H2L3)) are studied by electrochemical techniques, FE-SEM images and XRD patterns. Linear sweep voltammetry studies indicate that 2 and 3 have superior activities and only require the overpotential of 316 and 247 mV vs. RHE at current density of 10 mA/cm2 with Tafel slopes of 75 and 50 mVdec?1 at pH = 11. Experiments show relationships between the stability of the complexes and their catalytic activity. It is revealed that substituents on ligands affect the catalytic behaviors. Experiments show that in the presence of 2 and 3, the complexed cobalt ions are likely candidates as molecular catalysts for water oxidation. It is speculated that the O–O bond formation occurs by oxidizing the active center of cobalt complexes. 相似文献
39.
The effects of introducing La2NiO4 nanocatalyst on the electrochemical performance of La0.8Sr0.2MnO3 are investigated under solid oxide electrolysis cell and fuel cell modes, as well as open circuit voltage. Extracted data from impedance spectroscopy are interpreted with the analysis of distribution of relaxation times. La2NiO4 infiltration effectively reduces the activation energy of the oxygen reactions from 1.35 to 0.99 eV. It also changes the rate controlling process of the overall reaction. Polarization behavior of La2NiO4-infiltrated La0.8Sr0.2MnO3 electrode shows superior performance under electrolysis mode compared to the fuel cell mode. Drastic increase in the size of low frequency arc during anodic current passage in the non-infiltrated La0.8Sr0.2MnO3 electrode is hampered by infiltration of La2NiO4 nanocatalyst. By applying anodic current on infiltrated La0.8Sr0.2MnO3, no displacement is observed in the position of high frequency peaks in the distribution of relaxation time graphs and only a small increase in height occurs for the low frequency arc. Additionally, La2NiO4-infiltrated electrode impressively decreases overpotential by 74% compared to the non-infiltrated one under electrolysis mode at 800°C. 相似文献