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61.
Mohamad Javad Tahmasebi Birgani Fatemeh Seif Nahid Chegeni Mohamad Reza Bayatiani 《Journal of Radioanalytical and Nuclear Chemistry》2012,292(3):1367-1370
In consideration the radiological properties of materials and studying the scattering processes in atomic and nuclear physics,
the effective atomic and mass numbers is widely employed. These numbers have been calculated for any mixed or composite materials
in interaction with high energy photons (Linac in radiation therapy). A pair equation in terms of these numbers is obtained.
The first equation has been derived from the conservation of mass energy law and the second by minimizing the binding energy
from the semiempirical mass formula (Myers and Swiatecki formula) that gives a relation between atomic and mass numbers for
stable nuclei approximately. By these equations one can obtain the effective atomic and mass numbers for any compound or mixed
materials uniquely. These numbers are calculated for some materials and compared with the other studies. 相似文献
62.
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
63.
Soon-Lim ChongKhalijah Awang Marie Therese MartinMat Ropi Mokhtar Gomathi ChanMarc Litaudon Francoise GueritteKhalit Mohamad 《Tetrahedron letters》2012,53(40):5355-5359
Two structurally interesting novel limonoids, malayanine A and malayanine B, were isolated from the bark of Chisocheton erythrocarpus Hiern. The structures were fully characterized through spectroscopic methods. 相似文献
64.
A comparative study on chemical conversion of cellulose between the batch-type and flow-type systems in supercritical water 总被引:1,自引:0,他引:1
Microcrystalline cellulose (avicel) was treated in supercritical waterusing batch-type and flow-type systems. The flow-type system made it possibletoshorten the heating, treating and cooling times, compared with the batch-typesystem. As a result, the flow-type system was able to liquefy avicel withoutproducing any supercritical water-insoluble residue. Although hydrolyzedproducts such as glucose and fructose, and pyrolyzed products such aslevoglucosan, 5-hydroxymethyl furfural, erythrose, methylglyoxal,glycolaldehydeand dihydroxyacetone were found in common from the water-soluble portiontreatedby both systems, the flow-type system gave a water-soluble portion with morehydrolyzed and less pyrolyzed products, together with water-solubleoligosaccharides consisting of cellobiose to cellododecaose and theirdecomposedproducts at their reducing end of glucose, such as[–glucopyranosyl]1–11 –levoglucosan,[–glucopyranosyl]1–11 –erythrose and[–glucopyranosyl]1–11 –glycolaldehyde. Inaddition, the precipitates of polysaccharides were recovered after 12h setting of the water-soluble portion. These results indicatedthat the flow-type system can hydrolyze cellulose with minimizing pyrolyzedproducts. On the other hand, the batch-type system resulted in a higher yieldof the pyrolyzed products due to the longer treatment, but a higher yield ofglucose due possibly to the higher pressure and concomitantly higher ionicproduct of water. Based on these lines of evidence, the process to increase theyield of the sugar is discussed under supercritical water treatment. 相似文献
65.
Marble AE Mastikhin IV MacGregor RP Akl M LaPlante G Colpitts BG Lee-Sullivan P Balcom BJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,168(1):164-174
The results of a magnetic resonance imaging (MRI) investigation concerning the effects of an aluminum honeycomb sandwich panel on the B1 and B0 fields and on subsequent image quality are presented. Although the sandwich panel structure, representative of an aircraft composite material, distorts B0 and attenuates B1, distortion-free imaging is possible using single point (constant time) imaging techniques. A new expression is derived for the error caused by gradient field distortion due to the heterogeneous magnetic susceptibility within a sample and this error is shown not to cause geometric distortion in the image. The origin of the B0 distortion in the sample under investigation was also examined. The graphite-epoxy 'skin' of the panel is the principal source of the B0 distortion. Successful imaging of these structures sets the stage for the development of methods for detecting moisture ingress and degradation within composite sandwich structures. 相似文献
66.
In this paper, a new channel drop filter in two dimensional photonic crystals with mirror cavities is proposed. In the structure,
three cavities are used. One is used for a resonant tunneling-based channel drop filter. The others are used to realize reflection
feedback in the bus waveguide, which consists of a point defect micro-cavity side-coupled to a waveguide. The simulation results
by using the finite-difference time-domain method conclude 98% output efficiency. 相似文献
67.
Y. G. Shee M. A. Mahdi M. H. Al-Mansoori A. Ismail N. A. M. A. Hambali A. K. Zamzuri R. Mohamad S. Yaakob 《Laser Physics》2009,19(12):2194-2196
A simple configuration for the reduction of stimulated Brillouin scattering threshold in photonic crystal fiber is presented.
The threshold reduction is contributed by the bidirectional pumping scheme through the reflection of transmitted Brillouin
pump back to the gain medium. The pump recycling scheme has greatly reduced the Brillouin threshold of a 200-m long of photonic
crystal fiber from 50 to 30 mW of Brillouin pump power. 相似文献
68.
Mohamad Sh. Ramadan Nabila M. El-Mallah Sherif M. Abd-Elmenem 《Journal of Dispersion Science and Technology》2013,34(8):1110-1120
AbstractThe interaction between anionic dyes [Reactive Orange 122 (R.O 122), Reactive Blue 19 (R.B 19), Reactive Violet 5 (R.V 5) and Acid Green 20 (A.G 20)] with cationic surfactant cetyltrimethylammoniun bromide (CTAB) has been investigated by spectrophotometry and conductance technique. The used dyes are characterized by tautomeric behavior which affects the mechanism of the interaction. Various parameters such as dye structure, surfactant composition, solvent composition, temperature and pH of the medium were studied. The spectral data were applied for calculating the binding constant between dye and surfactant (Kb), fraction of micellization (?mic), and standard free energy change of binding (ΔG°b) in 0,10,20 and 30 v/v % acetonitile (AN). Conductance technique was constructed to estimate the ion pairing constant (Ka) at different temperatures and v/v % AN. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) for ion pair formation were evaluated. The role of hydrophobic and electrostatic effect on dye-surfactant interaction was discussed. 相似文献
69.
S. Hosseini M. HomaieeA.B. Mohamad M.R. MalekbalaA.A.H. Khadum 《Physica B: Condensed Matter》2011,406(9):1689-1694
Cesium dihydrogen phosphate (CDP) nanoparticles were synthesized using the surfactants cetyltrimethyl ammonium bromide (CTAB), polyoxyethylene-polyoxypropylene (F-68) and (F-68:CTAB) with molar ratio 0.06. The samples conductivity such as CDPCTAB, CDPF-68 and CDP(F-68:CTAB)0.06 was studied by impedance spectroscopy in the frequency range 0.01 Hz to 1 MHz. The Nyquist plots were drawn at different temperatures of 210, 230 and 260 °C, which are defined below transition, phase transition and above transition, respectively. The measured conductivities obey the Arrhenius relation. The influence of surfactants on conductivity are more significant at higher temperature due to grain boundary. The conductivity of CDPCTAB increased slightly with increasing temperature to 260 °C, whereas the conductivity of other samples decreased with increasing temperature over 230 °C. The results indicated that the conductivities increase in the order of CDPCTAB>CDP(F-68:CTAB)0.06>CDPF-68. These are in accordance to the ion exchange capacities of the samples that the surfactant shows a direct influence on the samples proton mobility. It is found that the conductivity of CsH2PO4 is influenced by surfactant type. 相似文献
70.
Hossein Tavanai Rouholah Jalili Mohamad Morshed 《Surface and interface analysis : SIA》2009,41(10):814-819
The effects of fiber diameter and activation temperature on the pore characteristics of polyacrylonitrile based activated carbon nanofibers are investigated. It was found that lower fiber diameters as well as higher activation temperatures lead to a higher weight loss, specific surface area and total pore volume. The nitrogen adsorption capacity of activated carbon nanofibers is almost three times that of activated carbon fiber with a diameter of 10 µm. As far as the size of pores in activated carbon nanofibers is concerned, it is basically the micropores that dominate the scene. Moreover, tailoring the pore characteristics by adjusting the activation temperature and fiber diameter is plausible. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献