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排序方式: 共有97条查询结果,搜索用时 15 毫秒
1.
Amir Hamzeh Haghiabi 《Water Resources Management》2017,31(3):811-824
Modeling river mixing mechanism in terms of pollution transmission in rivers is an important subject in environmental studies. Dispersion coefficient is an important parameter in river mixing problem. In this study, to model and predict the longitudinal dispersion coefficient (D L ) in natural streams, two soft computing techniques including multivariate adaptive regression splines (MARS) as a new approach to study hydrologic phenomena and multi-layer perceptron neural network as a common type of neural network model were prepared. To this end, related dataset were collected from literature and used for developing them. Performance of MARS model was compared with MLP and the empirical formula was proposed to calculate D L . To define the most effective parameters on D L structure of obtained formula from MARS model and more accurate formula was evaluated. Calculation of error indices including coefficient of determination (R2) and root mean square error (RMSE) for the results of MARS model showed that MARS model with R2?=?0.98 and RMSE?=?0.89 in testing stage has suitable performance for modeling D L . Comparing the performance of empirical formulas, ANN and MARS showed that MARS model is more accurate compared to others. Attention to the structure of developed MARS and the most accurate empirical formulas model showed that flow velocity, depth of flow (H) and shear velocity are the most influential parameters on D L . 相似文献
2.
Hamzeh Agahi Adel Mohammadpour S. Mansour Vaezpour 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(4):659-666
In this paper, we give a generalization of the Chebyshev type inequalities for Sugeno integral with respect to non-additive
measures. The main results of this paper generalize most of the inequalities for Sugeno integral obtained by many researchers.
Also, some conclusions are drawn and some problems for further investigations are given. 相似文献
3.
This article presents an intelligent strategy to achieve appropriate real power sharing among distributed generators in a microgrid. The presented strategy employs two droop-based control methods and automatically adjusts their parameters. The first method is unit power control, which has specifications similar to the conventional droop method, and the second is feeder flow control, showing significant characteristics in both grid-connected and islanded modes operation of a microgrid. A combination of unit power control and feeder flow control methods is used for a multi-distributed generator microgrid. The microgrid operation mode passes from the grid-connected to the islanded through a transition. A new evolutionary algorithm called cuckoo search is employed to coordinate the power management of distributed generators within an on-line droop tuning. In comparison to the predecessor evolutionary algorithms, the cuckoo search algorithm represents more effective random processes with fewer parameters. Using the proposed control strategy, while the distributed generators contribute to load demand provision based on their rated powers, their powers are optimized in terms of overshoot and settling time. Digital time-domain simulation studies are carried out in the MATLAB/SIMULINK (The MathWorks, Natick, Massachusetts, USA) environment to verify the performance of the proposed control system. 相似文献
4.
Hamid Jadidi Hamzeh Shahrajabian Mehdi Moghri 《Journal of Inorganic and Organometallic Polymers and Materials》2016,26(4):881-888
Nanocomposite foams contain very fine cells because of the fillers in nano scale. Due to the limited size of the cells, the mechanical and physical properties of nanocomposite foams are improved compared to polymer foams. In this study PVC/clay nanocomposite foams containing various concentrations of nano-clay (1, 3 and 5 phr) were successfully prepared. The samples were placed under CO2 gas pressure at 5 MPa, by immersing in glycerin bath at 60, 70, 80 °C and 20, 30, 40 s, respectively, to form foams. The density and the cell size as a factor of nano-clay content, foaming time and temperature were investigated using Archimedes method and scanning electron microscopy, respectively. The minimum density was obtained in the sample containing 1 phr nanoclay prepared at 80 °C and 40 s. The minimum cell size was related to the sample containing 5 phr nanoclay at 60 °C and 20 s. 相似文献
5.
Ali Eatemadi Hadis Daraee Hamzeh Karimkhanloo Mohammad Kouhi Nosratollah Zarghami Abolfazl Akbarzadeh Mozhgan Abasi Younes Hanifehpour Sang Woo Joo 《Nanoscale research letters》2014,9(1):393
Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering. 相似文献
6.
Rahim Yadollahi Yahya Hamzeh Alireza Ashori Shademan Pourmousa Mohammad Jafari Kambiz Rashedi 《Polymer Engineering and Science》2013,53(1):183-188
Papermaking sludge (PS), a waste residue from the pulp and paper processing, has brought great pressure on the environment because of large quantities that are produced in paper mills. This work was carried out to explore the possibility of making PS/cement composite products using solid waste of PS. Boards measuring 350 × 270 × 12 mm3 were manufactured using PS contents of 40, 50, and 60 wt%, adhesive dosages of 0, 10, and 15 wt%, and 0 and 5 wt% of calcium chloride as an accelerator. At least three replications were fabricated for each treatment, and some mechanical and physical properties of the boards were evaluated. Test results showed that the bending and internal strengths of the specimens decreased with an increase in the PS content, and the maximum values were obtained at PS loading of 40 wt%. The negative influence of PS content on the mechanical properties can be explained by the reduced bonding ability because of weaker PS compared with cement. Screw withdrawal values were up to 22.7 kPa. Water absorption and thickness swelling of cement mortar considerably increased with increased content of PS, with a corresponding reduction of bulk density. In general, all properties of the boards were improved when the adhesive and calcium chloride contents were increased. The results showed that an increase in board density improved the mechanical and physical properties. Finally, results showed that PS has good potential for recycling and utilization in developing value‐added building components. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers 相似文献
7.
Multilayer assembly of ionic starches on old corrugated container recycled cellulosic fibers
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Hamidreza Rudi Yahya Hamzeh Esmaeil Rasooly Garmaroody Seyed Rahman Djafari Petroudy Mousa M Nazhad 《Polymer International》2018,67(1):85-90
In this study, old corrugated container recycled fibers were treated with polyelectrolyte multilayers consisting of biopolymer cationic starch with two degrees of substitution (DS) each in combination with one anionic starch. Pulp zeta potential, paper strength and the thin layer ellipsometry technique were applied to examine the influence of cationic starch DS on the formation of polyelectrolyte multilayers. The results indicated a significant interaction between the DS of cationic starch and the number of ionic starch layers formed. When low‐DS cationic starch was used, the pulp zeta potential and the paper strength increased significantly in assembling the first cationic layer. However, in depositing high‐DS cationic starch a greater zeta potential and a stronger influence on the paper strength were observed with a larger number of starch layers. This was confirmed by thin layer ellipsometry when a greater thickness of multilayers was achieved by employing high‐DS cationic starch to form a higher number of layers. © 2017 Society of Chemical Industry 相似文献
8.
Gang Huang Jiuhui Han Fan Zhang Ziqian Wang Hamzeh Kashani Kentaro Watanabe Mingwei Chen 《Advanced materials (Deerfield Beach, Fla.)》2019,31(2)
The key bottlenecks hindering the practical implementations of lithium‐metal anodes in high‐energy‐density rechargeable batteries are the uncontrolled dendrite growth and infinite volume changes during charging and discharging, which lead to short lifespan and catastrophic safety hazards. In principle, these problems can be mitigated or even solved by loading lithium into a high‐surface‐area, conductive, and lithiophilic porous scaffold. However, a suitable material that can synchronously host a large loading amount of lithium and endure a large current density has not been achieved. Here, a lithiophilic 3D nanoporous nitrogen‐doped graphene as the sought‐after scaffold material for lithium anodes is reported. The high surface area, large porosity, and high conductivity of the nanoporous graphene concede not only dendrite‐free stripping/plating but also abundant open space accommodating volume fluctuations of lithium. This ingenious scaffold endows the lithium composite anode with a long‐term cycling stability and ultrahigh rate capability, significantly improving the charge storage performance of high‐energy‐density rechargeable lithium batteries. 相似文献
9.
We propose a wireless optical-mesh network based on optical code-division multiple-access (OCDMA)-coded free-space optical links. The performance of the proposed network under intermediate and strong turbulence channel conditions is investigated for synchronous and asynchronous OCDMA. We show that synchronous OCDMA using complementary Walsh-Hadamard codes operating at a raw bit rate of 622 Mb/s per user can achieve a bit-error rate of 10/sup -9/. This is achievable in channels with strong turbulence and high temporal correlation, or in channels with intermediate turbulence conditions; reasonable conditions based on channel characteristics inferred from the refractive index spectrum. For asynchronous OCDMA using optical orthogonal codes (OOCs), using a lower bound, we show that asynchronous OCDMA using OOCs cannot achieve acceptable performance for the same channel conditions, due to interference limitations. 相似文献
10.
S. Hamzeh Javaran N. Khaji H. Moharrami 《Engineering Analysis with Boundary Elements》2011,35(1):85-95
In this paper, a new boundary element analysis for two-dimensional (2D) transient elastodynamic problems is proposed. The dual reciprocity method (DRM) is reconsidered by employing new radial basis functions (RBFs) to approximate the domain inertia terms. These new RBFs, which are in the form of ζ+κ sin (ωr+α), are called Fourier RBFs hereafter. Using the method of variation of parameters, the particular solution kernels of Fourier RBFs corresponding to displacement and traction, whose a few terms are singular, has been explicitly derived. Therefore, a new simple smoothing trick has been employed to resolve the singularity problem. Moreover, the limiting values of the particular solution kernels have been evaluated. In order to find the unknown parameters of Fourier RBFs, an optimization problem seeking for the optimum value of the Houbolt scheme parameter β that minimizes the mean squared error (MSE) function of the problem is established. Since the MSE function of the proposed RBFs is a function of five unknown parameters (i.e., ζ, κ, ω, α, and β), the genetic algorithm (GA) has been used to solve the necessary optimization problem. In order to illustrate the validity, accuracy, and superiority of the present study, several numerical examples are examined and compared to the results of analytical and other RBFs reported in the literature. Compared to other RBFs, Fourier RBFs show more accurate and stable results. Moreover, these results are obtained using less degree of freedom without any additional internal points that are commonly used to improve the accuracy of the results. 相似文献