Graduate University of Advanced Technology

About: Graduate University of Advanced Technology is a education organization based out in Kerman, Iran. It is known for research contribution in the topics: Carbon paste electrode & Electrochemical gas sensor. The organization has 890 authors who have published 2169 publications receiving 31027 citations.

Preparation and characterization of carbon nanotubes/pyrite nanocomposite for degradation of methylene blue by a heterogeneous Fenton reaction

Abstract: Carbon nanotubes/pyrite (CNTs/FeS2) nanocomposite was prepared by the co-precipitation of ferrous and ferric salts in presence of CNTs and subsequent sulfuration treatment of the prepared carbon nanotubes/iron oxide (CNTs/Fe3O4) material with elemental sulfur. The resulting nanocomposite was well characterized using FE-SEM, TEM, XRD, EDS and TGA techniques. The CNTs/FeS2 nanocomposite was employed as a heterogeneous catalyst for degradation of methylene blue (MB) dye in aqueous solution. The influence of reaction conditions including the hydrogen peroxide (H2O2) amount, hydroxylamine (NH2OH) amount, initial pH value and catalyst dosage on the dye degradation were studied. The degradation efficiency of MB (100 mg L − 1) was up to 99.5% when the pH value, H2O2 amount, NH2OH amount and catalyst dosage were 3.0, 200 μL, 60 mg and 0.2 g, respectively. Beside, the positive effect of NH2OH on MB degradation is caused by the acceleration of Fe3+ ions reduction and enhancement the oxidation reactivity in the Fenton system. The reusability of the catalyst was also studied after six successive cycles. In addition, an oxidation mechanism of MB by the present Fenton process was proposed. The present system has advantages on the viewpoint of high degradation performance, no sludge formation, short reaction time and catalyst reusability.

Quantum Zeno and anti-Zeno effects on the entanglement dynamics of qubits dissipating into a common and non-Markovian environment

Abstract: We investigate the quantum Zeno and anti-Zeno effects on pairwise entanglement dynamics of a collective of noninteracting qubits which have been initially prepared in a Werner state and are off-resonantly coupled to a common and non-Markovian environment. We obtain the analytical expression of the concurrence in the absence and presence of the nonselective measurements. In particular, we express our results in the strong and weak coupling regimes and examine the role of the system size and the effect of the detuning from the cavity field frequency on the temporal behavior of the pairwise entanglement. We show that the detuning parameter has a positive role in protection of entanglement in the absence of the measurement for the weak coupling regime. We find that for the values of detuning parameter less than the cavity damping rate, the quantum Zeno effect is always dominant, while for values greater than the cavity damping rate, both Zeno and anti-Zeno effects can occur, depending on the measurement intervals. We also find that the anti-Zeno effect can occur in the pairwise entanglement dynamics in the absence and presence of the detuning in the strong coupling regime.

Spatial contribution of one-day precipitations variability to rainy days and rainfall amounts in Iran

Abstract: Rainfalls with short persistency are the tangible characteristics of arid and semiarid regions such as Iran. Iran is an arid and semiarid region with dramatic tempo-spatial changes of rainfall. In this regard, the short persistency of rainfall is approximately observed from 1 to 7 days in whole parts, while the greater ones are only separated in eastern parts of Iran. According to the results, the rainfall persistency is ranged from 1 to 45 days, but the maximum amount and rainy days are generated by rainfalls with short persistency. So, the rainfall events with long persistency are considered as an extreme event with extreme variability. One-day precipitations generate the maximum rainy days and rainfall amounts, especially in eastern parts of Iran. Decrease in the one-day precipitations contribution to eastern parts may indicate to decrease in regional precipitation. However, decrease in contribution in western parts may indicate to increased amounts of rainfall at other persistency rates. Our results revealed that the contribution of the one-day precipitation to general rainfall has reductive trends in almost 17.5 % of the whole Iran. The most integrated and significant reductive trend of one-day precipitation contribution to rainfall spreads northeastern and eastern parts of Iran. However, in the western parts of Iran, decreasing one-day precipitation contribution to rainy days affects to increase in the diurnal rainfall. The mentioned variability can be considered as the climate change signals in respect of one-day precipitation.

Application of response surface methodology for optimization of metal-organic framework based pipette-tip solid phase extraction of organic dyes from seawater and their determination with HPLC.

Abstract: This paper describes the application of response surface methodology (RSM) to develop a miniaturized metal organic framework based pipette-tip solid phase extraction for the extraction of malachite green (MG), rhodamine B (RB), methyl orange (MO) and acid red 18 (AR) dyes from seawater samples and their determination by high performance liquid chromatography. The effects of various parameters such as pH of the sample solution, type and amount of added salt, type and volume of eluent solvent, concentration of surfactant (triton X-114), sample volume, and number of cycles of extraction and desorption were investigated and optimized by two methods of one-variable-at-a-time and RSM based on Box–Behnken design. Under optimum conditions, the linear range of the method was 0.5–200.0 µg/L for RB and MG and 1.0–150.0 µg/L for AR and MO. Limits of detection of the analytes were obtained in the range of 0.09–0.38 µg/L. Reproducibility of the method (as RSD %) was better than 6.4%. The method has been successfully used for analysis of four dyes in seawater of Chabahar Bay.

Unified Performance Analysis of Multi-Hop FSO Systems Over Double Generalized Gamma Turbulence Channels With Pointing Errors

Abstract: Free space optical (FSO) communication systems provide high bandwidth in unregulated spectrum and act as a powerful line-of-sight wireless connectivity solution. The performance of FSO systems can be seriously impaired by fading as a result of atmospheric turbulence and/or pointing errors due to misalignment. In the context of FSO systems, relaying was proposed as an effective fading mitigation technique due to the fact that the variance is distance-dependent in turbulence channels. In this article, we present a unified performance analysis of multi-hop FSO systems over Double Generalized Gamma (DGG) turbulence channels with pointing error impairments. We assume amplify-and-forward relaying and consider both heterodyne detection and intensity modulation with direct detection. We derive tight closed-form expressions for the outage probability and bit error probability of both fixed-gain and channel state information (CSI)-assisted relaying in terms of the bivariate Fox-H functions and Fox-H functions, respectively. We further analyze asymptotic behavior of the outage probability in terms of simple elementary functions and obtain the achievable diversity orders. Diversity gain is found to be a function of atmospheric turbulence parameters, pointing error, detection type and the number of hops. Monte Carlo simulation results are further provided to verify the accuracy of the derived expressions.