Sharif Digital Repository

Green and simple synthesis strategies have gained tremendous popularity for the production of anisotropically-shaped noble metallic nanoparticles. The long-term stability of the produced particles, the short timescale of the target reaction(s), as well as the use of non-toxic chemicals, are pivotal features of a useful green procedure. Herein we describe a simple and convenient wet-chemical approach to synthesize stable, non-toxic and water-soluble small gold nanotriangles (GNTs) and gold nanospheres (GNSs) in one step at room temperature, using Tween 20 and Tween 80, respectively. A high level of purity and monodispersity was obtained for the GNTs, in addition to an excellent colloidal... 

Phased array antennas are generally used for the inherent flexibility to beamforming and null-steering electronically. In the phased arrays the side lobes level (SLL) level is main problem which causes waste of energy or saturation of the receiver in the case of presence of the strong spatial blockers. In this paper, a weighting method was first used to reduce the level of SLL. However, this method increased the beam width and reduced resolution, which is not suitable for track applications. In next step hoping to increase the resolution, the distance between the antennas increased. But in this way, grating lobes appeared in the final beam. In fact, the main idea of the article is to solve... 

In this paper the design of a digital step attenuator with simultaneous low phase and gain error characteristics is investigated. First, the loading effect of the consecutive blocks of an N-bit attenuator on the precision of the attenuation levels is analyzed. Then a modified structure to decrease the loading effect as well as the phase error of the attenuator blocks is presented. A comprehensive analysis of the circuit is performed and some design guidelines have described. Finally, a 6-bit attenuator with attenuation range of 0.5–31.5 dB and resolution of 0.5 dB is implemented in 0.18 µm complementary metal–oxide-semiconductor (CMOS) technology. The root mean square (RMS) gain error and...