Comparison Study of Pattern Synthesis Techniques Using Neural Networks

In this paper, a comparison study among three neuralnetwork algorithms for the synthesis of array patterns is presented. The neural networks are used to estimate the array elements' excitations for an arbitrary pattern. The architecture of the neural networks is discussed and simulation results are presented. Two new neural networks, based on radial basis functions (RBFs) and wavelet neural networks (WNNs), are introduced. The proposed networks offer a more efficient synthesis procedure, as compared to other available techniques

Synthesis, Characterisation and Properties of (Ba1-xSrx) (Nd1/2Nb1/2 ) 03 Ceramics for Application as Dielectric Resonators in Microwave Circuits

The (Ba1-x Srx) (Nd1/2, Nb1/2) O3 ceramics have been prepared by the conventional ceramic route for different values of x. Addition of a small amount of CeO2(1 wt%) as a sintering aid increased the density of the samples. The structure and microstructure of the sintered samples are studied by X-ray diffraction and SEM methods. The dielectric properties of the samples are measured in the microwave frequency region as a function of composition. The dielectric constant decreases as x increases. The coefficient of thermal variation of resonant frequency decreases as the Sr content increases and goes to the negative side. The dielectric properties of (Ba1-x Srx) (Nd1/2, Nb1/2) O3 are in the range suitable for application as dielectric resonators in microwave circuits

Synthesis,Characterization and Properties of [REI_xREX]TiNb06 Dielectric Ceramics

Dielectric ceramics based on solid solution phases of [RE1_x= REr]TiNb06, where REI_s = Nd, Pr, Sm and RE' = Dy, Gd and Y, were prepared by the conventional solid-state ceramic route for values of x. The ceramic samples are characterized by X-ray diffraction and microwave methods. Ceramics based on RE (Pr, Nd and Sm) belonging to aeschynite group shows positive value of Tf and those based on RE (Gd, Dy and Y) belonging to euxenite group show negative value of r f. The solid solution phases between the aeschynite and the euxenite group shows intermediate dielectric constant and r f values. The results indicate the possibility of tailoring the dielectric properties by varying the composition of the solid solution phases. The range of solid solubility of euxenite in aeschenite and aeschenite in euxenite are different for different rare earth ions

Synthesis, Characterization and Properties of Ca5A2TiO12 (A=Nb, Ta) Ceramic Dielectric Materials for Applications in Microwave Telecommunication Systems

Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Q5 x f > 30000GHz) and small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator applications in microwave integrated circuits. [DOI: 10. 1 143/JJAP.41.3834]

Synthesis, characterization, and structure of a new cobalt(II) Schiff-base complex with quinoxaline- 2-carboxalidine-2-amino-5-methylphenol

The mononuclear cobalt(II) complex [CoL2] H2O (where HL is quinoxaline-2-carboxalidine- 2-amino-5-methylphenol) has been prepared and characterized by elemental analysis, conductivity measurement, IR, UV-Vis spectroscopy, TG-DTA, and X-ray structure determination. The crystallographic study shows that cobalt(II) is distorted octahedral with each tridentate NNO Schiff base in a cis arrangement. The crystal exhibits a 2-D polymeric structure parallel to [010] plane, formed by O-H...N and O-H... O intermolecular hydrogen bonds and pye stacking interactions, as a racemic mixture of optical enantiomers. The ligand is a Schiff base derived from quinoxaline-2-carboxaldehyde

Synthesis, characterization and hydrodesulphurisation activity of CoMo/gama-Al2O3 catalyst prepared through molecular designed dispersion method

CoMo/gama-Al2O3 catalysts for hydrodesulphurisation activity were prepared by making use of the molecular designed dispersion (MDD) method. Molybdenum and cobalt pyrrolidine-N-carbodithioate (Pydtc) complexes were used for the incorporation of metals on the support. The catalysts were characterized by elemental analysis, low temperature oxygen chemisorption, temperature programmed reduction (TPR) and laser Raman spectroscopy. The hydrodesulphurisation activity of all the catalysts were carried out and results were compared with those of the catalysts prepared through the conventional method. Higher molybdenum dispersion, smaller molybdenum clusters, lower reduction temperature of catalyst and better hydrodesulphurisation activity were observed for the catalysts prepared through the MDD method

Synthesis and Characterization of Some New Transition Metal Complexes of the Schiff Base Derived from Quinoxaline-2-Carboxaldehyde and 2- Aminophenol

Some new transition metal complexes of the Schiff base quinoxaline-2-car boxalidene-2-aminophenol (HQAP) have been synthesized and characterized by elemental analyses, conductance and magnetic measurements and IR and UV-Visible spectral studies. The complexes have the following empirical formulae: [Mn(QAP121, [Fe(QAPl2C1I, [Co(QAPl21, [Ni(QAP121 and [Cu(QAP121. A tetrahedral structure has been assigned for the manganese(=), cobalt(II1, nickel(II1 and copper(II1 complexes. For the iron(IIIl complex an octahedral dimeric structure has been suggested