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排序方式: 共有373条查询结果,搜索用时 15 毫秒
21.
Five types of multiwalled carbon nanotubes noncovalently functionalized with poly (propylene imine) dendrimer (PPI (G2))-silver nanoparticle hybrids were prepared by varying the [Ag+] load from 2 to 6 mM. These nanohybrids were characterized with FTIR, UV-Vis, FESEM, EDS, HRTEM and Raman analyses. The catalytic potential was studied through the reduction of 4-nitrophenol as a model reaction under pseudo first-order reaction conditions. The calculated kobs value (16.94 × 10?2 min?1) reveals that the 4 mM [Ag+] loaded catalyst showed higher efficiency than with rest of the catalysts. Further, the in vitro antimicrobial activities of all nanohybrids were inspected against Pseudomonas aeruginosa and Staphylococcus aureus. 相似文献
22.
Thermal behavior of crude oil (Fosterton) asphaltenes mixed with reservoir sand was investigated using thermogravimetric analysis (TGA), in nitrogen and air atmospheres for different heating rates up to 800 °C. In this study, four sets of TGA runs were performed to examine the thermal behavior of Fosterton asphaltenes and the coke derived from the asphaltenes. The parameters studied were heating rate (10, 15 and 20 °C min− 1) and the type of purge gas (N2 and air) employed for the process of thermal degradation of asphaltenes. Distributed activation energy model (DAEM) has been applied to study the asphaltene pyrolysis kinetics. It was observed that the activation energy was distributed from 46.16 to 72.17 kJ/mol, for the conversion range of 0.1 to 0.4. The general model for nth order reaction was used to obtain the kinetic parameters of coke oxidation reaction from the TGA data. From the model, the calculated activation energy, E, was 93.46 kJ/mol and the pre-exponential factor was 9.59 × 105 min− 1 for the coke combustion. The apparent order of combustion reaction gradually increased from 0.7 to 0.8 for different temperatures. 相似文献
23.
I. Dinaharan N. Murugan Siva Parameswaran 《Materials Science and Engineering: A》2011,528(18):5733-5740
Particulate reinforced metal matrix composites (PMMCs) have gained considerable amount of research emphasis and attention in the present era. Research is being carried out across the globe to produce new combination of PMMCs. PMMCs are prepared by adding a variety of ceramic particles with monolithic alloys using several techniques. An attempt has been made to produce aluminium metal matrix composites reinforced with zirconium boride (ZrB2) particles by the in situ reaction of K2ZrF6 and KBF4 salts with molten aluminium. The influence of in situ formed ZrB2 particles on the microstructure and mechanical properties of AA6061 alloy was studied in this work. The in situ formed ZrB2 particles significantly refined the microstructure and enhanced the mechanical properties of AA6061 alloy. The weight percentage of ZrB2 was varied from 0 to 10 in steps of 2.5. Improvement of hardness, ultimate tensile strength and wear resistance of AA6061 alloy was observed with the increase in ZrB2 content. 相似文献
24.
The present study was evaluated using the following in vitro antioxidant methods: 2,2′-azinobis (3-ethyl-benzothiozoline)-6-sulfonic acid disodium salt, phosphomolybdenum, ferric reducing antioxidant power, metal ion chelating activity, super oxide anion radical scavenging, hydrogen peroxide, and hydroxyl radical. Among these assays, acetone extract showed maximum free radical scavenging activity in 2,2′-azinobis (3-ethyl-benzothiozoline)-6-sulfonic acid disodium salt, phosphomolybdenum, metal ion chelating, superoxide anion, hydrogen peroxide, and hydroxyl radical assays. Moreover, the physiochemical, nutritional, and anti-nutritional parameters were analyzed. Its qualitative and quantitative composition was studied by gas chromatography-mass spectroscopy and out of 27 peaks, 27 compounds were identified. These compounds have the property of antioxidant, antimicrobial, and anti-inflammatory activity. 相似文献
25.
Application of Sequential Learning Neural Networks to Civil Engineering Modeling Problems 总被引:1,自引:0,他引:1
A sequential orthogonal approach to the building and training of a single hidden layer neural network is presented in this
paper. The Sequential Learning Neural Network (SLNN) model proposed by Zhang and Morris [1]is used in this paper to tackle
the common problem encountered by the conventional Feed Forward Neural Network (FFNN) in determining the network structure
in the number of hidden layers and the number of hidden neurons in each layer. The procedure starts with a single hidden neuron
and sequentially increases in the number of hidden neurons until the model error is sufficiently small. The classical Gram–Schmidt
orthogonalization method is used at each step to form a set of orthogonal bases for the space spanned by output vectors of
the hidden neurons. In this approach it is possible to determine the necessary number of hidden neurons required. However,
for the problems investigated in this paper, one hidden neuron itself is sufficient to achieve the desired accuracy. The neural
network architecture has been trained and tested on two practical civil engineering problems – soil classification, and the
prediction o strength and workability of high performance concrete. 相似文献
26.
A. Vadivel Murugan A. B. Gaikwad V. Samuel V. Ravi 《Bulletin of Materials Science》2006,29(3):221-223
An aqueous mixture of ammonium oxalate and ammonium hydroxide was used to coprecipitate barium and strontium ions as oxalates
and niobium ions as hydroxide under basic conditions. This precursor on calcining at 750°C yielded Sr0.5Ba0.5Nb2O6 phase. This is a much lower temperature than that prepared by traditional solid state method (1000°C) as reported for the
formation of Sr0.5Ba0.5Nb206 (SBN). Transmission electron microscopic (TEM) investigations revealed that the average particle size was 80 nm for the calcined
powders. The room temperature dielectric constant at 1 kHz was found to be 1100. The ferroelectric hysteresis loop parameters
of these samples were also studied. 相似文献
27.
Jerusha A. Hema Rajkumari Malaka Narayanan P. Muthukumarasamy Akilandeswari Sambandam Subakanmani Subramanian Murugan Sevanan 《IET nanobiotechnology / IET》2016,10(5):288
The biosynthesis of silver nanoparticles (AgNPs) has been proved to be a cost effective and environmental friendly approach toward chemical and physical methods. In the present study, biosynthesis of AgNPs was carried out using aqueous extract of Zea mays (Zm) husk. The initial colour change from golden yellow to orange was observed between 410 and 450 nm which confirmed the synthesis of AgNPs. Also, dynamic light scattering‐particle size analysis confirmed the average size to be 113 nm and zeta potential value of −28 kV. The morphology of synthesised Zm AgNPs displayed flower‐shaped structure, X‐ray diffraction pattern revealed the strongest peaks at 2θ = 38.6° and 64° which proved that the nanoparticle has the face centred crystalline structure. The Fourier transform infrared spectroscopy results showed strong absorption bands at 1394.53, 2980.02 and 2980.02 cm−1 due to the presence of alkynes, carboxylic acids, alcoholic and phenolic groups. The maximum zone of inhibition was observed against Salmonella typhi (22 mm) and Candida albicans (18 mm). The synthesised nanoparticles exhibited more free radical scavenging activity than the aqueous plant extract. This is the first report on the synthesis of AgNP from Zm husk, delivers the efficient and stable Zm AgNPs through simple feasible approach toward green biotechnology.Inspec keywords: silver, nanoparticles, nanofabrication, light scattering, particle size, X‐ray diffraction, crystal structure, Fourier transform infrared spectra, absorption coefficients, free radicalsOther keywords: green synthesis, silver nanoparticles, biosynthesis, environmental friendly approach, aqueous extract, Zea mays husk, colour change, golden yellow, dynamic light scattering‐particle size analysis, average size, zeta potential value, flower‐shaped structure, X‐ray diffraction pattern, face centred crystalline structure, Fourier transform infrared spectroscopy, absorption bands, alkynes, carboxylic acids, alcoholic groups, phenolic groups, Salmonella typhi, Candida albicans, free radical scavenging activity, aqueous plant extraction, green biotechnology, size 113 nm, wavelength 410 nm to 450 nm 相似文献
28.
Thermogravimetric analysis (TGA) was used to examine the thermal behavior of Fosterton oil mixed with reservoir sand. TGA experiments were performed in nitrogen and air atmospheres at the heating rate of 10 °C/min up to 800 °C. In this study, four sets of TGA runs were performed to examine the thermal behavior of Fosterton whole oil, and the coke sample derived from the whole oil. Similar to previous studies in the literature, we also observed low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO) in the non-isothermal combustion experiment. Higher activation energy values were obtained in reaction regions at higher temperatures. The mean activation energy for whole oil in nitrogen and air atmospheres was 33 and 126 kJ/mol, respectively. Fresh coke samples derived from whole oil were subjected to isothermal combustion at different temperatures from 375 to 500 °C. Arrhenius model was used to obtain the kinetic parameters from the TGA data. From the model, the Arrhenius parameters such as activation energy (E = 127 kJ/mol) and the pre-exponential factor (A = 1.6 × 108/min) were determined for the coke combustion. The results showed a close agreement between the kinetic model and experimental data for different combustion temperatures. It was observed that the apparent order of combustion reaction for different temperatures approach unity. 相似文献
29.
30.
Transparent glasses of lithium tetraborate (Li2B4O7) were prepared by a splat quenching technique. X-ray powder diffraction (XRD) and high resolution transmission electron microscopic studies revealed the amorphous nature of the as-quenched samples. The glassy nature of these samples was confirmed by differential thermal analysis. Physical properties such as density, dielectric and ac conductivity have been studied. Glasses of Li2B4O7 exhibit a dielectric anomaly close to the crystallization temperature which is attributed to the interfacial polarization caused by Li+ ion motion within the borate network. 相似文献