排序方式: 共有98条查询结果,搜索用时 78 毫秒
41.
42.
43.
44.
Fahimeh Emadi Ali Nemati Manuel Hinterstein Esmaeil Adabifiroozjaei 《Ceramics International》2019,45(5):5503-5510
In the present work the effect of simultaneous doping of carbon and nickel on the microstructural, optical, and electrical properties of barium strontium titanate (BST) is investigated. Thin films of BST were prepared by the sol-gel method in six different compositions ((Ba0.6Sr0.4)(NixCyTi1-x-y)O3): x?=?y?=?0.00 (BST), x?=?0.04?y?=?0.00 (BST4N), x?=?0.04?y?=?0.01 (BST4N-1C), x?=?0.04?y?=?0.02 (BST4N-2C), x?=?0.04?y?=?0.03 (BST4N-3C), and x?=?y?=?0.04 (BST4N-4C). Structural features and chemical bonds of the films were studied by TGA/DSC, XRD, FT-IR, and FE-SEM. The electrical and optical properties of the films were analysed by impedance spectroscopy and UV–VIS spectroscopy. The results show that addition of Ni and C leads to Ti4+-Ni2+ and Ti4+-C4+ replacements, respectively. These replacements lead to a gradual increase in the band gap energy; from 3.15?eV for BST to 3.44, 3.5, 3.66, 3.73 and 3.76?eV for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. In contrast, the dielectric loss decreases significantly from 0.055 for BST to 0.031, 0.033, 0.03, 0.022 and 0.01 for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. At the same time, the quality factor Qf (1/ tanδ) increases substantially from 15 for BST to 32, 30, 33, 44 and 87 for BST4N, BST4N-1C, BST4N-2C, BST4N-3C, and BST4N-4C, respectively. In contrast, the frequency dependence of the capacity decreases in comparison to un-doped BST. Among all films, the BST4N-4C had the highest figure of merit (FOM), least dielectric loss, and very low frequency-dependence, making it the best candidate for tuneable device applications. 相似文献
45.
Fahimeh Sadat Mohammadi Daryush Arabian 《Journal of the American Oil Chemists' Society》2023,100(1):45-56
The aim of this study was to determine and optimize culture media for Chlorella vulgaris microalgae under mixotrophic conditions using waste molasses as a cheap carbon source containing both organic carbons and other nutrients. In the current study, at first the growth and lipid productivity of C. vulgaris were assessed in different culture media and the best media was selected for mixotrophic growth conditions. Significant medium ingredients were screened through Plackett–Burman design. Then ingredients with positive effect were considered as a mixture component and their combinations were evaluated on lipid productivity using mixture design. According to results, Zarrouk medium was considered as the base medium with the highest biomass and lipid productivity of 72 and 7.1 mg L−1 d−1, respectively. Based on the Plackett–Burman design, out of 11 factors, molasses, NaNO3 and K2HPO4 demonstrated key roles in biomass and lipid productivity in mixotrophic conditions. Consequently, the selected three factors were investigated by mixture design. The results showed that high concentration of molasses causes decrease in biomass and lipid productivity due to high turbidity and a blend consisting of approximately 9.5 g L−1 molasses, 5 g L−1 NaNO3 and 0.15 g L−1 K2HPO4 was found as the optimum mixture with obtained lipid productivity of 115 mg L−1 d−1. In conclusion, waste molasses can be used as a promising feedstock for cost effective cultivation of C. vulgaris. 相似文献
46.
Monolayers of methyl-undecanoate were constructed on silicon surfaces via a covalent Si-C bond. The molecular monolayers were characterized by high resolution electrical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and ellipsometry and displayed a densely packed monolayer. After formation of the monolayer, the methyl ester was hydrolyzed without noticeable change in the integrity of the monolayer. The carboxyl terminated organic layer was then reacted with (1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide to form active N-hydroxy succinimide ester groups. The activation chemistry was confirmed by XPS and the substructure of the methyl-undecanoate carboxylic acid and the N-hydroxy succinimide ester terminated films were characterized using EIS. XPS and EIS spectra provided information on the chemical composition and substructure of the monolayers for each step in the chemical modification of the surface. 相似文献
47.
Fahimeh Darki Mohammad Ali Oghabian Alireza Ahmadian Hamid Soltanian Zadeh Mojtaba Zarei 《International journal of imaging systems and technology》2011,21(4):307-314
Tractography is one of the most important applications of diffusion tensor imaging (DTI) which noninvasively reconstructs 3D trajectories of the white matter tracts. Because of the intravoxel orientation heterogeneity of DTI data, some of tractography algorithms are unable to follow the correct pathways after the crossing and branching regions. Front propagation techniques are efficient methods in tracking the crossing fibers. A key parameter influencing the performance of these algorithms is the cost function which is mainly based on the colinearity of tensors' eigenvectors. The effect of the eigenvalues on the anisotropy strength of tensor has not been previously addressed in the definition of the speed function. In this article, a new speed function, based on the effect of diffusion anisotropy and the colinearity of eigenvectors is proposed. The performance of the suggested method on fiber tracking and crossing fiber detection has been evaluated using synthetic datasets, and the feasibility of the proposed method was shown by fiber tracking implemented on real DTI data. © 2011 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 21, 307–314, 2011 相似文献
48.
Fahimeh Khaksar-Haghani Reza Kia Iraj Mahdavi Mohammad Kazemi 《The International Journal of Advanced Manufacturing Technology》2013,66(5-8):845-865
This paper presents a novel integer linear programming model for designing multi-floor layout of cellular manufacturing systems (CMS). Three major and interrelated decisions are involved in the design of a CMS; namely cell formation (CF), group layout (GL), and group scheduling (GS). A novel aspect of this model is concurrently making the CF and GL decisions to achieve an optimal design solution in a multi-floor factory. Other compromising aspects are: multi-floor layout to form cells in different floors is considered, multi-rows layout of equal area facilities in each cell is allowed, cells in flexible shapes are configured, and material handling cost based on the distance between the locations assigned to machines are calculated. Such an integrated CMS model with an extensive coverage of important manufacturing features has not been proposed before and this model incorporates several design features including alternative process routings, operation sequence, processing time, production volume of parts, duplicate machines, machine capacity, new machine purchasing, lot splitting, material flow between machines, intra-cell layout, inter-cell layout, multi-floor layout and flexible configuration. The objective is to minimize the total costs of intra-cell, inter-cell, and inter-floor material handling, new machines purchasing and machine processing. Two numerical examples are solved by the Lingo software to verify the performance of the proposed model and illustrate the model features. Sensitive analysis is also implemented on some model parameters. An improved genetic algorithm (GA) is proposed to derive near-optimal solutions for the integrated model because of its NP hardness. It is then tested using several problems with different sizes and settings to verify the computational efficiency of the developed algorithm in comparison to a classic simulated annealing algorithm and the Lingo software. The obtained results show the efficiency of proposed GA in terms of objective function value and computational time. 相似文献
49.
Immobilization of biomaterials onto solid supports is a means of functionalizing materials for applications such as biosensing. Biologically active peptide (A-A-A-A-G-G-G-E-R-G-D)1 films were attached to N-hydroxy succinimide ester terminated self-assembled monolayers (SAM) which were covalently linked to a smooth silicon surface via Si–C bonds. The peptide films were characterized using electrical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The film structures were determined from examination of the capacitance and conductance dispersions with frequency. Analysis of XPS, EIS and FTIR after immobilization of the peptide film at pH 4 and 7 provided information on the extent of the activation and overall coupling efficiencies of the peptides to the N-hydroxy succinimide ester surface. The resulting film structure was markedly altered by attachment of the peptide at pH 4. 相似文献
50.
Many analytical and numerical analysis and design methods for geosynthetic-reinforced soil structures require a single-value (constant) estimate of reinforcement stiffness. However, geosynthetic reinforcement products are rate-dependent polymeric materials meaning that they exhibit time and strain-dependent behaviour under load. Hence, the appropriate selection of a constant (elastic) stiffness value requires careful consideration. A simple hyperbolic stiffness model is shown to be a useful approximation to the constant-load isochronous creep-strain behaviour of these materials at low load levels applicable to operational (serviceability) conditions of geosynthetic-reinforced soil structures. A large database of 606 creep tests on 89 different geosynthetic reinforcement products falling within seven different product categories was collected. From these data, isochronous stiffness values were determined for different combinations of duration of loading and strain level. Data from products falling within the same category were collected together to provide approximations linking the isochronous load-strain (creep) stiffness to the ultimate tensile strength of the material. These approximations are useful for analytical and numerical modelling particularly when parametric studies are undertaken to identify the sensitivity of model outcomes to reinforcement stiffness. Finally, three different geosynthetic-reinforced soil application examples are provided to demonstrate the important role of tensile stiffness on analysis and design outcomes. 相似文献