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排序方式: 共有190条查询结果,搜索用时 15 毫秒
91.
Erfan Abedi Esfahani Hamidreza Salimijazi Mohamad A. Golozar Javad Mostaghimi Larry Pershin 《Journal of Thermal Spray Technology》2012,21(6):1195-1202
In the current study, aluminum coating was deposited on mild steel by arc spraying. A well-adhered coating with low level of porosity was successfully obtained. To evaluate the corrosion behavior of the coating, electrochemical impedance spectroscopy (EIS) and polarization tests in 3.5% NaCl solution were carried out. The as-coated samples were also subjected to a 1500-h salt spray assay. Polarization tests indicated that the corrosion current density of the aluminum coating is more than that of bulk aluminum. This could be due to the penetration of the electrolyte through open pores, resulted in the acceleration of aluminum corrosion. EIS measurements showed that the corrosion performance of the coating is improved during a long time immersion and exposure to saline mist. This could be due to plugging of pores by corrosion products which hinder further penetration of the electrolyte through the coating. The results obtained indicated that twin wire arc sprayed aluminum coatings can reliably protect steel structures against corrosion in chloride-containing aqueous solutions. 相似文献
92.
93.
水敏性硅烷改性聚氨酯粘合剂 总被引:8,自引:3,他引:5
本文研究了水敏性硅烷改性聚氨酯粘合剂的配方及合成工艺条件并考查了其对玻璃-玻璃、玻璃-铁、铁-铁的粘接性能。 相似文献
94.
In this study, thermomechanical vibration analysis of functionally graded (FG) nanobeams subjected to in-plane thermal loads are carried out by presenting a Navier-type solution and employing a semi-analytical differential transform method (DTM) for the first time. Two types of thermal loading, namely, linear and non-linear temperature rises through the thickness direction are considered. Thermomechanical properties of FG nanobeam are supposed to vary smoothly and continuously throughout the thickness based on power-law model and material properties are assumed to be temperature-dependent. Eringen non-local elasticity theory is exploited to describe the size dependency of FG nanobeam. Using Hamilton's principle, the non-local equations of motion together with corresponding boundary conditions are obtained for the free vibration analysis of FG nanobeams including size effect and they are solved applying DTM. According to numerical results, it was revealed that the proposed modeling and semi-analytical approach can provide accurate frequency results of the FG nanobeams as compared to analytical results and also some cases in the literature. A parametric study is included to examine the effects of several parameters, such as temperature rise, gradient index, small-scale parameter and boundary conditions on the normalized natural frequencies of the temperature-dependent FG nanobeams in detail. It is explicitly shown that the vibration behaviour of a FG nanobeams is significantly influenced by these effects. The new results can be used as benchmark solutions for analyses of FG nanobeams. 相似文献
95.
Erfan Zalnezhad Saeid Baradaran A. R. Bushroa Ahmed A. D. Sarhan 《Metallurgical and Materials Transactions A》2014,45(2):785-797
With the intention of improving the mechanical properties of Ti-6Al-4V, samples were first coated with pure titanium using the physical vapor deposition (PVD) magnetron sputtering technique. The Taguchi optimization method was used to attain a higher coating on substrate adhesion. Second, pure titanium-coated samples with higher adhesion were anodized to generate TiO2 nanotubes. Next, the TiO2-coated specimens were heat treated at annealing temperatures of 753.15 K and 923.15 K (480 °C and 650 °C). The XRD results indicate that the varying heat treatment temperatures produced different phases, namely, anatase [753.15 K (480 °C)] and rutile [923.15 K (650 °C)]. Finally, the coated samples’ mechanical properties (surface hardness, adhesion, and fretting fatigue life) were investigated. The fretting fatigue lives of TiO2-coated specimens at 753.15 K and 923.15 K (480 °C and 650 °C) annealing temperatures were significantly enhanced compared to uncoated samples at low and high cyclic fatigue. The results also indicate that TiO2-coated samples heat treated at an annealing temperature of 753.15 K (480 °C) (anatase phase) are more suitable for increasing fretting fatigue life at high cyclic fatigue (HCF), while at low cyclic fatigue, the annealing temperature of 923.15 K (650 °C) seemed to be more appropriate. The fretting fatigue life enhancement of thin-film TiO2 nanotubular array-coated Ti-6Al-4V is due to the ceramic nature of TiO2 which produces a hard surface as well as a lower coefficient of friction of the TiO2 nanotube surface that decreases the fretting between contacting components, namely, the sample and friction pad surfaces. 相似文献
96.
M. H. Korayem A. M. Shafei F. Absalan B. Kadkhodaei A. Azimi 《The International Journal of Advanced Manufacturing Technology》2014,71(5-8):1005-1018
This paper presents an investigation into the development of modeling of n-viscoelastic robotic manipulators. The dynamic model of the system is derived using Gibbs-Appell formulation and assumed mode method. When the beam is short in length direction, shear deformation is a factor that may have significant effects on system dynamic. So, in modeling, the assumption of Timoshenko beam theory and associated mode shapes has been considered. Although including the effect of damping in continuous systems makes the formulations more complicated, two important damping mechanisms, namely, Kelvin-Voigt damping as internal damping and the viscous air damping as external damping have been considered. Based on derived formulation, a non-linear recursive algorithm is developed for deriving the inverse dynamic equation of motion, systematically. The performance of the proposed algorithm was assessed in terms of the required mathematical operations for deriving the kinematic and dynamic equations of the mechanical system. Finally, to validate the proposed formulation, a comparative assessment between the results achieved from experiment and simulation is presented in time and frequency domains. 相似文献
97.
Mohammad Mahdi Hasani-Sadrabadi Erfan DashtimoghadamFatemeh S. Majedi Shahriar Hojjati EmamiHomayoun Moaddel 《International Journal of Hydrogen Energy》2011,36(10):6105-6111
A novel double layer proton exchange membrane (PEM) comprising a layer of structurally modified chitosan, as a methanol barrier layer, coated on Nafion®112 was prepared and assessed for direct methanol fuel cell (DMFC) applications. Scanning electron microscope (SEM) micrographs of the designed membrane revealed a tight adherence between layers, which indicate the high affinity of opposite charged polyelectrolyte layers. Proton conductivity and methanol permeability measurements showed improved transport properties of the designed membrane compared to Nafion®117. Moreover, DMFC performance tests revealed a higher open circuit voltage and power density, as well as overall fuel cell efficiency for the double layer membrane in comparison with Nafion®117, especially at elevated methanol solution feed. The obtained results indicate the designed double layer membrane as a promising PEM for high-performance DMFC applications. 相似文献
98.
Diagnostic Utility of Genome-Wide DNA Methylation Analysis in Mendelian Neurodevelopmental Disorders
Sadegheh Haghshenas Pratibha Bhai Erfan Aref-Eshghi Bekim Sadikovic 《International journal of molecular sciences》2020,21(23)
Mendelian neurodevelopmental disorders customarily present with complex and overlapping symptoms, complicating the clinical diagnosis. Individuals with a growing number of the so-called rare disorders exhibit unique, disorder-specific DNA methylation patterns, consequent to the underlying gene defects. Besides providing insights to the pathophysiology and molecular biology of these disorders, we can use these epigenetic patterns as functional biomarkers for the screening and diagnosis of these conditions. This review summarizes our current understanding of DNA methylation episignatures in rare disorders and describes the underlying technology and analytical approaches. We discuss the computational parameters, including statistical and machine learning methods, used for the screening and classification of genetic variants of uncertain clinical significance. Describing the rationale and principles applied to the specific computational models that are used to develop and adapt the DNA methylation episignatures for the diagnosis of rare disorders, we highlight the opportunities and challenges in this emerging branch of diagnostic medicine. 相似文献
99.
Silicon - Heavy metal pollution is one problem in the water purification industry, which causes extreme risk aversion. The purpose of this study was to investigate the removal of arsenic (As) and... 相似文献
100.
Wireless Networks - The performance of mobile ad hoc networks (MANETs) is significantly affected by the malicious nodes. One of the most common attacks in MANETs is denial of service (DoS); a type... 相似文献