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131.
Ibrahim Palabiyik Zenfira Musina Sanjeeva Witharana Yulong Ding 《Journal of nanoparticle research》2011,13(10):5049-5055
The dispersion stability and thermal conductivity of propylene glycol-based nanofluids containing Al2O3 and TiO2 nanoparticles were studied in the temperature range of 20–80 °C. Nanofluids with different concentrations of nanoparticles
were formulated by the two-step method and no dispersant was used. In contrast to the common belief, the average particle
size of nanofluids was observed to decrease with increasing temperature, and nanofluids showed an excellent stability over
the temperature range of interest. Thermal conductivity enhancement for both studied nanofluids was a nonlinear function of
concentration and was temperature independent. Theoretical analyses were also performed using existing models compared with
experimental results. The model based on the aggregation theory appears to be the best. 相似文献
132.
133.
Wee Ching Tan Siti Salwa Alias Ahmad Badri Ismail Ahmad Azmin Mohamad 《Journal of Solid State Electrochemistry》2012,16(6):2103-2112
The effect of a gel polymer electrolyte (GPE) as the redox electrolyte used in dye-sensitized solar cells was studied. A GPE solution consisting of 0.5?M sodium iodide, 0.05?M iodine, and ethylene carbonate/propylene carbonate (1:1 w/w) binary solvents was mixed with increasing amounts of styrene–acrylonitrile (SAN). Bulk conductivity measurements show a decreasing trend from 4.54 to 0.83×10?3?S?cm?1 with increasing SAN content. The GPE exhibits Newtonian-like behavior and its viscosity increases from 0.041 to 1.093?Pa?s with increasing SAN content. A balance between conductivity (1.3?×?10?3?S?cm?1) and viscosity (1.4?Pa?s) is observed at 19?wt.% SAN. Fourier transform infrared spectroscopy detects elevated ring torsion at 706?cm?1 upon the addition of SAN into the liquid electrolyte. This indicates that SAN does not bond with the liquid electrolyte. Finally, the potential stability window of 19?wt.% SAN, which ranges from ?1.68 to 1.38?V, proves its applicability in solar cells. 相似文献
134.
Alaa A. Hassan Yusria R. Ibrahim Essmat M. El‐Sheref Ashraf A. Aly Stefan Bräse Alan B. Brown 《Journal of heterocyclic chemistry》2012,49(6):1380-1385
1‐Substituted 3‐[3‐(methyl/phenyl)‐1H‐pyrazol‐5‐yl]thioureas react with the triple bond of dimethyl acetylenedicarboxylate forming (Z)‐methyl 2‐[(Z)‐3‐substituted‐2‐(3‐(methyl/phenyl‐1H‐pyrazol‐5‐ylimino)‐4‐oxothiazolidin‐5‐ylidene)acetates. Rational for these conversations are presented. 相似文献
135.
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137.
The manner is investigated in which exergy-related parameters can be used to minimize the cost of a copper–chlorine (Cu–Cl) thermochemical cycle for hydrogen production. The iterative optimization technique presented requires a minimum of available data and provides effective assistance in optimizing thermal systems, particularly in dealing with complex systems and/or cases where conventional optimization techniques cannot be applied. The principles of thermoeconomics, as embodied in the specific exergy cost (SPECO) method, are used here to determine changes in the design parameters of the cycle that improve the cost effectiveness of the overall system. The methodology provides a reasonable approach for improving the cost effectiveness of the Cu–Cl cycle, despite the fact that it is still in development. It is found that the cost rate of exergy destruction varies between $1 and $15 per kilogram of hydrogen and the exergoeconomic factor between 0.5 and 0.02 as the cost of hydrogen rises from $20 to $140 per GJ of hydrogen energy. The hydrogen cost is inversely related to the exergoeconomic factor, plant capacity and exergy efficiency. The results are expected to assist ongoing efforts to increase the economic viability and to reduce product costs of potential commercial versions of this process. The impact of the results are anticipated to be significant since thermochemical water splitting with a copper–chlorine cycle is a promising process that could be linked with nuclear reactors to produce hydrogen with no greenhouse gases emissions, and thereby help mitigate numerous energy and environment concerns. 相似文献
138.
A nonlinear finite element model is provided to predict the static aero-thermal deflection and the vibration behavior of geometrically imperfect shape memory alloy hybrid composite panels under the combined effect of thermal and aerodynamic loads. The nonlinear governing equations are obtained using Marguerre curved plate theory and the principle of virtual work taking into account the temperature-dependence of material properties. The effect of large deflection is included in the formulation through the von Karman nonlinear strain-displacement relations. The thermal load is assumed to be a steady-state constant-temperature distribution, whereas the aerodynamic pressure is modeled using the quasi-steady first-order piston theory. The Newton-Raphson iteration method is employed to obtain the nonlinear aero-thermal deflections, while an eigenvalue problem is solved at each temperature step and static aerodynamic load to predict the free vibration frequencies about the deflected equilibrium position. Finally, the nonlinear deflection and free vibration characteristics of a composite panel are presented, illustrating the effects of geometric imperfection, temperature rise, aerodynamic pressure, boundary conditions and shape memory alloy fiber embeddings on the panel response. 相似文献
139.
We report what is to our knowledge the first demonstration of all-optical time-division demultiplexing and spatial pulse routing in a compact nonlinear GaAs/AlGaAs microring resonator operating at 1.55 microm . Switching is through the refractive-index change induced by two-photon absorption. The switching time of the device, limited by the ring-charging time and the recombination time of the induced carriers, is measured to be 30 ps. The switching on-off contrast, limited by the slight mismatch between the input and output coupling coefficients, exceeds 8 dB. The device can be used for time-division multiplexing as well. 相似文献
140.
Ibrahim I. A. ElSersy H. H. Abadir M. F. 《Journal of Thermal Analysis and Calorimetry》2004,76(3):713-718
Thermal analysis was first used to investigate the pattern of dissociation of hydrated ordinary Portland cement. Portlandite
(Ca(OH)2) decomposes at about 500°C. This was confirmed by kinetic calculations. Thermal analysis was then performed to establish
the effect of varying the cement content on the percent mass loss associated with the decomposition of Ca(OH)2 in cement mortar cured for 28 days. An increasing relation was obtained. Standard concrete cubes were then prepared with
cement contents ranging from 200 to 450 kg m-3. The loss in mass on heating, up to 750°C, of concrete samples cured for 28 days was then related to the cement content in
concrete. The relation obtained was tested for concrete cubes of known cement content and found to be in better agreement
than the results obtained by conventional chemical analysis. This method can be used for an approximate determination of the
cement content in concrete.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献