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991.
A new method for determination of cyclamate was developed using headspace single-drop microextraction (HS-SDME) and gas chromatography (GC). The method is based on the reaction of cyclamate and nitrite in the acidic media and microextraction of cyclohexene formed for subsequent determination with GC. Conditions for both derivatisation and HS-SDME have been optimised. The calibration curve for cyclamate determination showed good linearity in the range of 30–1000 μmol L−1 (R2 = 0.9992) and the limit of detection (S/N = 3) was estimated to be 5 μmol L−1. The repeatability and reproducibility for a 200 μmol L−1 of cyclamate were 4% and 4.8% (N = 5), respectively. The purposed method was successfully applied for determination of cyclamate in beverages and sweetener tablets. The average recovery of spiked samples was 97%. The results demonstrated that the developed method is simple, rapid, inexpensive, accurate and remarkably free from interference effects. 相似文献
992.
Emad Khaksar Mahdi Shafiee Afarani Abdolreza Samimi 《Journal of Materials Engineering and Performance》2014,23(1):92-100
Synthesis of nanostructure titania powders and in situ crystallization of anatase coating layer on sintered alumina granules by solvothermal method were investigated. In coating process, addition of polyvinyl alcohol (PVA) as binder to solvothermal solution was also studied. Microstructure analyses of powders showed that crystallization and growth of nanostructure anatase phase in a thin gel layer were enhanced with temperature increase. The titania nanopowders synthesized at 120 °C and 8 h represented photodegradation of methyl orange solution as model wastewater up to maximum 94% yield in slurry photoreactor. However, in coating process, with increasing temperature to 220 °C and coating time to 24 h, adhesion and photocatalytic properties of the coated layer were improved. Furthermore, PVA binder addition led to formation of more uniform layer with less attrition loss in the reactor. 相似文献
993.
Nader Rahemi Mohammad Haghighi Ali Akbar Babaluo Mahdi Fallah Jafari Sirous Khorram 《International Journal of Hydrogen Energy》2013
Ni/Al2O3 nanocatalysts doped with Co and Cu were prepared by co-impregnation and modified by non-thermal plasma. The nanocatalysts were characterized by XRD, FESEM, TEM, EDX dot-mapping, BET, FTIR, TGA-DTG, and XPS analysis. According to XRD and XPS results, good interaction between active phase and support can be observed in both Ni–Co/Al2O3 and Ni–Cu/Al2O3 nanocatalysts. A uniform morphology, high surface area, and well dispersed particles of active sites in Ni–Co/Al2O3 nanocatalyst were observed that shows the effect of cobalt in controlling Ni ensemble size. In contrast Ni–Cu/Al2O3 nanocatalyst had no homogenous dispersion of active phase due to sintering of copper particles. The activity measurements illustrated better Ni–Co/Al2O3 nanocatalyst activity in comparison to Ni/Al2O3 and Ni–Cu/Al2O3 in terms of CH4 and CO2 conversion. H2 and CO yield were higher for Ni–Co/Al2O3 and higher H2/Co ratio was obtained as well. Whereas Ni/Al2O3 and Ni–Co/Al2O3 did not experience deactivation, Ni–Cu/Al2O3 suffered from activity loss by ca. 22% and 16% for CH4 and CO2 conversion, respectively. Sintering most likely happened in Ni–Cu/Al2O3 nanocatalyst due to high temperature of calcination while cobalt by controlling the size of Ni particles, alternated the size of active sites to a size range in which carbon formation was suppressed. Ni/Al ratio from XPS analysis which signifies Ni dispersion on alumina support was 5.15, 9.16, and 6.35 for Ni/Al2O3, Ni–Co/Al2O3, and Ni–Cu/Al2O3 nanocatalysts respectively. The highest ratio of Ni/Al was for Ni–Co/Al2O3 nanocatalyst that shows the best coverage of support by Ni active phase in this nanocatalyst. 相似文献
994.
Nazanin Rahimi Mohammad Mahdi Doroodmand Samad Sabbaghi Mohammad Hossein Sheikhi 《Materials science & engineering. C, Materials for biological applications》2013,33(6):3173-3179
Hydrogen evolution of multi-walled nanotube (MWCNT)/micro-hybrid polymer composite, decorated with Ni nanoparticles through electroless deposition process is studied by the electrochemical method. Cyclic voltammetry (CV) is utilized to clearly study the electrochemical hydrogen storage/evolution behavior of the composite through a potential window ranging from ? 1.60 to + 0.60 V (vs. Ag/AgCl). Hydrogen adsorption/desorption peaks are positioned at ? 1.52 and ? 0.05 V, respectively. Chronoamperometry is also applied to estimate active surface area (0.145 m2 g? 1) of the composite as well as the diffusion coefficient (3.4 × 10? 11 m2 s? 1) of adsorbed hydrogen process. According to the chrono-charge/discharge technique, the capacity of fabricated Ni-MWCNT/micro-hybrid composite is estimated to be 2.98 wt.% during charging for a certain time (40 min). 相似文献
995.
Alireza Karimi Mahdi Navidbakhsh Ahmad Shojaei Shahab Faghihi 《Materials science & engineering. C, Materials for biological applications》2013,33(5):2550-2554
Atherosclerosis is a common arterial disease which alters the stiffness of arterial wall. Arterial stiffness is related to many cardiovascular diseases. In this investigation, maximum stress and strain as well as physiological and maximum elastic modulus of 22 human coronary arteries are measured. In addition, the force-displacement diagram of human coronary artery is obtained to discern the alterations between the healthy and atherosclerotic arterial wall stiffness. The age of each specimen and its effect on the elastic modulus of human coronary arteries is also considered. Twenty-two human coronary arteries, including eight atherosclerotic and fourteen healthy arteries are excised within 5 hours post-mortem. Samples are mounted on a tensile-testing machine and force is applied until breakage occurs. Elastic modulus coefficient of each specimen is calculated to compare the stiffness of healthy and atherosclerotic coronary arteries. The results show that the atherosclerotic arteries bear 44.55% more stress and 34.61% less strain compared to the healthy ones. The physiological and maximum elastic moduli of healthy arteries are 2.53 and 2.91 times higher than that of atherosclerotic arteries, respectively. The age of specimens show no correlation with the arterial wall stiffness. A combination of biomechanics and mathematics is used to characterize the mechanical properties of human coronary arteries. These results could be utilized to understand the extension and rupture mechanism of coronary arteries and has implications for interventions and surgeries, including balloon-angioplasty, bypass, and stenting. 相似文献
996.
H.K. Hisham A.F. Abas G.A. Mahdiraji M.A. Mahdi A.S. Muhammad Noor 《Journal of Modern Optics》2013,60(4):393-401
A comprehensive study on the phase noise characteristics of a single-mode fiber grating Fabry–Perot (FGFP) laser was conducted numerically. Adding to previous studies, the effects of external optical feedback (OFB), external cavity length, temperature, injection current, cavity volume, nonlinear gain compression factor and fiber grating parameters on phase noise characteristics are presented. The temperature dependence (TD) of phase noise was calculated according to the TD of laser parameters and not by the well-known Parkove equation. The frequency spectra of FGFP laser phase noise were calculated by using a Fourier transform. Results show that the TD of the phase noise in FGFP lasers is smaller than that for distributed feedback lasers. The shortest external cavity length that provides the minimum phase noise is found to be around 3.1?cm. In addition, the relaxation oscillation frequency shifts towards more than 6?GHz, which provides larger flat frequency range. Furthermore, phase noise can be eliminated either by increasing the injection current or the OFB level. 相似文献
997.
Mohammad Mahdi A. Shirazi Meisam Tabatabaei 《Chemical Engineering Communications》2013,200(4):457-466
This article considers the application of the sweeping gas membrane distillation process (SGMD) for direct separation of ethanol-water using a flat sheet PTFE membrane. It also studies the effect of operating parameters including feed concentration, feed temperature, feed flow rate, and sweeping gas flow rate on the permeation flux and selectivity of ethanol/water. The results showed that the increase in feed temperature increases in permeate flux and selectivity. Selectivities of 18.5 to 25 were achieved using dilute feeds within the temperature range of 35 to 55°C. However, by increasing the feed concentration by more than 5 wt.%, the selectivity was decreased. The increase in permeation flux and ethanol selectivity at higher feed flow rates was mainly due to the reduction of polarization effects. Moreover, the PTFE membrane was characterized by AFM. The results showed that the present process could be used as a stand-alone technique for bioethanol process integration. 相似文献
998.
Mehdi Bahiraei Seyed Mostafa Hosseinalipour Mahdi Saeedan 《Chemical Engineering Communications》2013,200(2):260-268
Heat transfer and flow field of water-Al2O3 nanofluid were simulated three-dimensionally in the shell-side of shell-and-tube heat exchanger with helical baffles. The effects of Reynolds number and volume fraction on heat transfer and pressure drop were evaluated. Increasing the volume fraction and Reynolds number intensified both heat transfer and pressure drop. Reduction of the Reynolds number increased the friction factor, but no considerable change was observed in the friction factor by increasing the volume fraction at constant Reynolds number. Heat transfer of the nanofluid revealed greater dependency on the volume fraction of particles at lower Reynolds numbers. Models of Nusselt number and friction factor were obtained in the heat exchanger in terms of Reynolds number and volume fraction using neural network. The neural network predicted the output variables with great accuracy. 相似文献
999.
Mahdi Nasibi Milad Mohammady Ali Ashrafi Ali Akbar Dehno Khalaji Masoud Moshrefifar Elyas Rafiee 《Journal of Adhesion Science and Technology》2013,27(20):2001-2015
In this study, the effect of Turmeric (Curcuma Longa) extract (TE), as an environmentally friendly corrosion inhibitor, was investigated in 1?M hydrochloric acid solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Additionally, the proposed inhibitor was characterized by FTIR, and surface morphology of mild steel after and before its exposure to acid solution in the presence and absence of 0.030?g/l TE inhibitor was examined through scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), and atomic force microscopy (AFM) techniques. Effect of TE concentration and temperature was evaluated. Then, thermodynamic parameters have been calculated and adsorption studies have been investigated. A good fit to Freundlich adsorption isotherm was obtained between surface coverage degree and inhibitor concentration. SEM and AFM images and EDS analysis of mild steel specimens in the absence and presence of the TE inhibitor confirmed the protective layer formation on metal surface. Finally, electrostatic interaction between main component of inhibitor and metal surface was investigated. Inhibition efficiency up to 92% has been achieved in 1?M acid solution containing 0.030?g/l inhibitor at 22?°C. Neural network modeling shows low stability of TE by increasing temperature and time. 相似文献
1000.
Mohammad Mahdi Abolhasani Qipeng Guo Azam Jalali‐Arani Hossein Nazockdast 《应用聚合物科学杂志》2013,130(2):1247-1258
A phase diagram of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) was plotted, and the effects of the extent of miscibility on the mechanical properties of the polymer blends were examined. A compressible, regular solution model was used to forecast the phase diagram of this blend. The model prediction, the lower critical solution temperature (LCST) over the upper critical solution temperature (UCST), was done qualitatively according to the experimentally determined phase diagram by differential scanning calorimetry (DSC), optical microscopy, and rheological analysis. These experimental methods showed that this system was miscible in ACM‐rich blends (>50% ACM) and partially miscible in PVDF‐rich blends. A wide‐angle X‐ray diffraction study revealed that PVDF/ACM blends such as neat PVDF had a characteristic α‐crystalline peak. The partially miscible blends displayed up to 350% elongation at break; this was a significant increment of this parameter compared to that of neat PVDF(20%). However, the miscible blends showed elongation of up to 1000% [again, a remarkable increase compared to chemically crosslinked ACM (220%)] and displayed excellent mechanical properties and tensile strength and a large elongation at break. For the miscible and partially miscible blends, two different mechanisms were responsible for this improvement in the mechanical properties. It was suggested that in the partially miscible blends, the rubbery depletion layer between the spherulite and the conventional rubber cavitations mechanism were responsible for the increase in the elongation at break, whereas for the miscible blends, the PVDF spherulite acted as a crosslinking junction. The stretched part of the tensile samples in the partially miscible blends showed characteristic β‐crystalline peaks in the Fourier transform infrared spectra, whereas that in the miscible blends showed α‐crystalline peaks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1247‐1258, 2013 相似文献