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排序方式: 共有383条查询结果,搜索用时 15 毫秒
51.
Omnia M. El-Ahwany Ateyya A. Aboul-Enein Samira M. Abdel-Azim Noha A.K. Aboul-Gheit Salah A. Abo-EL-Enein 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(6):435-445
AbstractIn this study, Fe–MgO catalyst substrates with various Fe and MgO combinations were evaluated for the growth of different types of carbon nanostructure materials (CNMs), particularly graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) via chemical vapor deposition using methane as a carbon source. The hydrogen yield was also determined as a valuable by-product in this process. Therefore, a set of Fe–MgO catalysts with different iron loadings (30, 80, 85, 90 and 100?wt %) were prepared by the combustion method to realize this target. The physicochemical properties of freshly calcined Fe–MgO catalysts were investigated by XRD, TPR and BET, while the as-grown CNMs were studied by HR-TEM, XRD and Raman spectroscopy. The results verified that the morphology of as-grown CNMs as well as the H2 yield was directly correlated to the iron content in the catalyst composition. The XRD and TPR results showed that various FeMgOx species with deferent levels of interactions were produced with the gradual incorporation of MgO content. TEM images indicated that GNPs were individually grown on the surface of high loaded iron-containing catalysts (90–100?wt %) due to the presence of highly aggregated iron particles. While multi-walled carbon nanotubes (MWCNTs) with uniform diameters were grown on the low iron-loaded catalyst (30%Fe/MgO) due to the formation of highly dispersed FeMgOx particles. On the other hand, GNPs/MWCNTs hybrid materials were grown on the surface of 80%Fe and 85%Fe/MgO catalysts. This behavior can be interpreted by the co-existence of highly aggregated and highly dispersed Fe2O3 particles in the catalyst matrix. The results demonstrated that the catalyst composition has a notable effect on the nature of CNMs products and H2 yield. 相似文献
52.
Reza Tavakkoli-Moghaddam Samira Vazifeh-Noshafagh Ata Allah Taleizadeh Vahid Hajipour Amin Mahmoudi 《工程优选》2017,49(1):136-160
This article presents a new multi-objective model for a facility location problem with congestion and pricing policies. This model considers situations in which immobile service facilities are congested by a stochastic demand following M/M/m/k queues. The presented model belongs to the class of mixed-integer nonlinear programming models and NP-hard problems. To solve such a hard model, a new multi-objective optimization algorithm based on a vibration theory, namely multi-objective vibration damping optimization (MOVDO), is developed. In order to tune the algorithms parameters, the Taguchi approach using a response metric is implemented. The computational results are compared with those of the non-dominated ranking genetic algorithm and non-dominated sorting genetic algorithm. The outputs demonstrate the robustness of the proposed MOVDO in large-sized problems. 相似文献
53.
The present work reports the synthesis of ZnFe2O4 and ZnO-Zn1-xMxFe2O4+δ (Ln?=?Sm, Eu and Ho) nanomaterials by conventional solid state reactions between Ln2O3, Zn(NO3)2, Fe(NO3)3·9H2O and/or FeCl3·6H2O raw materials at 800?°C for 10?h and 15?h. Stoichiometric and nonstoichiometric reactions were explored for the synthesis of ZnFe2O4. The two Fe sources (Fe(NO3)3 and FeCl3) were used to study the proper raw material type for the synthesis of the ZnFe2O4. The synthesized nanomaterials were characterized by powder X-ray diffraction (PXRD) technique. Rietveld analysis showed that the obtained materials were crystallized well in cubic crystal system with the space group Fd3m and lattice parameters a?=?b?=?c?=?8.4?Å. The rietveld data showed that the purity of ZnFe2O4 was increased from 14% to 88% when the Fe source was changed from FeCl3 to Fe(NO3)3 meanwhile the reaction time was changed from 10 to 15?h. However, the purity was increased to 96% when the stoichiometry of Zn:Fe was changed from 1:2 to 0.8:2 at 800?°C for 15?h. The PXRD data revealed that dopant ion type had a considerable influence on the crystal phase purity of the obtained materials. It was found that Yb2O3 decreased more the purity of the obtained target compared to the other dopant ions. Ultraviolet-visible spectra showed that the synthesized nanomaterials had strong light absorption in the visible light region. Photocatalytic performance of the as-synthesized ZnFe2O4 was investigated for the degradation of pollutant Malachite Green (MG) in aqueous solution under direct visible light irradiation. The degradation yield at the optimized condition (0.09?mL H2O2, 30?mg catalyst and 60?min) was 98%. 相似文献
54.
Ehteram Mohammad Ghotbi Samira Kisi Ozgur EL-Shafie Ahmed 《Water Resources Management》2019,33(15):5207-5230
Water Resources Management - Water allocation is an important issue for systems with multiple stakeholders. Individual and collective decisions are very important for such systems. Thus, a new... 相似文献
55.
Complementary proteomic approaches reveal mitochondrial dysfunction,immune and inflammatory dysregulation in a mouse model of Gulf War Illness 下载免费PDF全文
56.
Maghraoui S Ayadi A Audinot JN Ben Ammar A Jaafoura MH El Hili A Migeon HN Tekaya L 《Microscopy research and technique》2012,75(2):182-188
The subcellular behavior of aluminum and indium, used in medical and industrial fields, was studied in the gastric mucosa and the liver after their intragastric administration to rats, using, two of the most sensitive methods of observation and microanalysis, the transmission electron microscopy, and the secondary ion mass spectrometry. The ultrastructural study showed the presence of electron dense deposits, in the lysosomes of parietal and principal gastric mucosa cells but no loaded lysosomes were observed in the different studied hepatic territories. The microanalytical study allowed the identification of the chemical species present in those deposits as aluminum or indium isotopes and the cartography of their distribution. No modification was observed in control rats tissues. In comparison to previous studies describing the mechanism of aluminum concentration in the gastric mucosa and showing that this element was concentrated in the lysosomes of fundic and antral human gastric mucosa, our study provided additional informations about the types of cells involved in the phenomenon of concentration of aluminum and indium, which are the parietal and the principal cells of the gastric mucosa. Our study demonstrated that these cells have the ability to concentrate selectively aluminum and indium in their lysosomes, as a defensive reaction against intoxication by foreign elements. 相似文献
57.
Saleheh?Abbaspoor Samira?Agbolaghi Farhang?AbbasiEmail author 《Polymer Bulletin》2017,74(4):1103-1119
Nano-channel single crystals were developed via consecutive growth of various polymer single-crystal channels comprising homo and block copolymers by self-seeding method. Poly(ethylene glycol)-b-polystyrene (PEG-b-PS) and poly(ethylene glycol)-b-poly(methyl methacrylate) (PEG-b-PMMA) block copolymers were synthesized by atom transfer radical polymerization. Self-seeding temperature, concentration, and crystallization time affected the width of the channels. This might provide a new way to investigate directional absorption, diffusion, and immobilization of biomacromolecules on the surface. The crystalline blocks of PEG-b-PS and PEG-b-PMMA diblock copolymers were similar, therefore, the continuity of channel-wire growth was guaranteed. Development of complete square channels next to the channels covered with high molecular weight brushes was infeasible. It was ascribed to a higher hindrance of primarily existing tethered chains on the single-crystal channel. Finally, the consecutive channel-wire single crystals were compared with single-step-grown pyramidal and conic structures. These multilayer crystals grew spirally and formed non-flat channels. The structure and morphology of different crystalline channels were detected by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). In this work, for the first time, the SAXS data of channel-wire single crystals were reported and they were compared by non-flat channel-like crystals. A profound investigation of PEG-b-PS, PEG-b-PMMA copolymers and PEG homopolymer channel-wire single crystals by SAXS and their comparison with AFM data was a novel work in the field of single-crystal engineering. 相似文献
58.
Jasem M. Al-Awadhi Raafat F. Misak Samira S. Omar 《Bulletin of Engineering Geology and the Environment》2003,62(2):107-115
Desertification in Kuwait is a process of environmental degradation under fragile ecological conditions and intensive human
activities and the consequences of Gulf War. In Kuwait, very severe desertification prevails, due to increasing formation
of new active sandy bodies, deterioration of many areas of natural vegetation cover to less than 10%, and limited water resources
for large-scale forage production. Average annual desertified land in Kuwait is estimated to be 285 km2. In Kuwait, three indicators of land degradation are encountered. These are vegetation, soil, and surface hydrological changes.
Based on field measurements of soil compaction and vegetation changes, in the west Jahra area in the northern part of the
country, degradation levels were assessed. Results of these measurements show that the average infiltration rate in compacted
soil decreased by 53.8% in comparison with non-compacted soil, while the average soil penetration resistance in compacted
soil increased by 154.1% in comparison with non-compacted soil. The bulk density in open sites was 23.4% higher than that
in protected sites. The percentage of litter in open sites decreased by 77.3% in comparison with protected sites, while the
percentage of total vegetation in open sites decreased by 6.1% in comparison with protected sites.
Electronic Publication 相似文献
59.
60.
David Pratella Samira Ait-El-Mkadem Saadi Sylvie Bannwarth Vronique Paquis-Fluckinger Silvia Bottini 《International journal of molecular sciences》2021,22(19)
Rare diseases (RDs) concern a broad range of disorders and can result from various origins. For a long time, the scientific community was unaware of RDs. Impressive progress has already been made for certain RDs; however, due to the lack of sufficient knowledge, many patients are not diagnosed. Nowadays, the advances in high-throughput sequencing technologies such as whole genome sequencing, single-cell and others, have boosted the understanding of RDs. To extract biological meaning using the data generated by these methods, different analysis techniques have been proposed, including machine learning algorithms. These methods have recently proven to be valuable in the medical field. Among such approaches, unsupervised learning methods via neural networks including autoencoders (AEs) or variational autoencoders (VAEs) have shown promising performances with applications on various type of data and in different contexts, from cancer to healthy patient tissues. In this review, we discuss how AEs and VAEs have been used in biomedical settings. Specifically, we discuss their current applications and the improvements achieved in diagnostic and survival of patients. We focus on the applications in the field of RDs, and we discuss how the employment of AEs and VAEs would enhance RD understanding and diagnosis. 相似文献