Parameter estimation of autoregressive signals in presence of colored AR(1) noise as a quadratic eigenvalue problem

In this paper, we consider the problem of parameter estimation of autoregressive (AR) signals from observations corrupted with colored AR(1) noise. The proposed method is based on Yule-Walker equations. We express these equations as a quadratic eigenvalue problem and then the parameters of the signal and noise are estimated by solving this eigenvalue problem. We also apply the proposed method to the problem of sinusoidal frequency estimation in colored noise. The performance of the proposed algorithm is evaluated by computer simulation examples.     

A markov model for investigating the impact of IEEE802.15.4 MAC layer parameters and number of clusters on the performance of wireless sensor networks

Wireless Networks - In this paper, a new analytical model is presented for cluster-based sensor networks using the non-beacon-enabled mode of IEEE802.15.4 MAC protocol. To accurately investigate...     

Effect of suitable surfactant on the large scale preparation of WO3 nanorods for the synthesis of WS2 nanoparticles

WO3 nanorods with average dimension about 23 x 145 nm have been synthesized in gram quantities by a hydrothermal method. Effect of various surfactants on the WO3 nanorods morphology was investigated. The results demonstrated that the application of suitable surfactant (such as Triton X-100), leads to obtain obviously individual morphology for WO3 nanorods (with average dimensions about 15 x 100 nm) and decrease the reaction time from 7 days to 3 days. With a very suitable and safe method, the as-prepared WO3 nanorods, will turn to WS2 nanoparticles by mixing them with Sulfur (S) powder, under reducing H2 atmosphere and high temperature. Therefore, application of the harmful and poisonous H2S gas was eliminated.     

Two-dimensional noisy autoregressive estimation with application to joint frequency and direction of arrival estimation

The present study addresses the problem of two-dimensional autoregressive estimation in the presence of additive white noise. The estimation method is based on combining the low-order and high-order Yule-Walker equations. The noise-compensated YW equations are solved using an iterative algorithm. The proposed method is also applied to joint frequency and direction of arrival estimation in uniform linear arrays. Using simulation study, the performance of the proposed algorithm is evaluated and compared with other methods.     

Solubilization of multi walled carbon nanotubes under a facile and mild condition

Multi-walled carbon nanotubes (MWCNTs) functionalized with amino groups was prepared via chemical modification of carboxyl groups introduced on the carbon nanotube surfaces. Oxidation of MWCNTs was performed with ozone in aqueous phase and amidation of generated carboxylic groups, was occurred with amines in the presence of HATU as a coupling agent. Obtained functionalized MWCNTs are soluble in many common organic solvents. The functionalized MWCNTs were characterized in detail using FTIR-ATR, Raman CHN and SEM methods.     

Porous nitrogen-doped graphene prepared through pyrolysis of ammonium acetate as an efficient ORR nanocatalyst

In the work presented here, a facile approach for the preparation of nitrogen-doped porous graphene was applied for the first time using ammonium acetate as a nitrogen rich precursor via pyrolysis at 900 °C for 2 h.The physicochemical properties of the prepared samples were determined using Field Emission Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectroscopy (EDS) mapping, Raman spectroscopy and X–ray photoelectron spectroscopy (XPS). The prepared samples were further applied for the oxygen reduction reaction (ORR) in alkaline solution, and the electrochemical performance was investigated and compared with porous graphene and Pt/C 20 wt.%. The results revealed that introducing nitrogen to the graphene structure leads to improvement in catalytic activity, enhanced catalytic current as well as more positive potential. Furthermore, N-doped graphene prepared using ammonium acetate exhibited excellent methanol tolerance and long-term stability. Finally, it was shown that the optimal pyrolysis temperature was obtained at 900 °C. Therefore, it is concluded that ammonium acetate could be used as an effective precursor for the ORR.