Theoretical and experimental analyses of rheological,compatibility and mechanical properties of PVMQ/XNBR-g GMA/XNBR/GO ternary hybrid nanocomposites

Iranian Polymer Journal - Effects of graphene oxide (GO) on various properties of rubber hybrid nanocomposites based on PVMQ/XNBR-g-GMA/XNBR (phenyl-vinyl-methyl-polysiloxane/carboxylated nitrile...     

Carbon nanotube based miniaturized electron gun and column assembly

We report on the application of silicon micromachining for the fabrication of miniaturized electron gun (MEG) assembly using vertically aligned carbon nanotubes. The proposed MEG consists of two main parts of electron gun and the accelerating column. While the electron gun consists of carbon nanotubes grown on a silicon substrate acting as an electron emission source, the accelerating column is made of micromachined silicon wafers with 5 μm thick membranes operating as objective lenses. These two wafers are placed together and sealed using a three-dimensional packaging technique. The simulation and experimental results show the evolution of a narrow electron beam by applying a proper voltage to the anodes and objective lens. The diverging and focusing of the beam can be controlled by applying the proper voltage on electrostatic lenses. This structure could be suitable for low energy SEM devices and surface physics applications.     

Estimation of the critical properties of compounds using volume-based thermodynamics

The importance, yet scarcity of the critical constants of thermally unstable fluids warrants the development of reliable methods for the estimation of these essential thermodynamic properties. A thorough investigation undertaken in this study on 1,589 compounds belonging to 83 chemical classes, indicated that the ratio of critical temperature to critical pressure of both low and high molecular weight compounds could be well expressed in terms of their volumetric properties. In addition, two new methodologies are presented for estimating V_c, as well as an indirect approach for prediction of T_c from surface tension data, altogether allowing the calculation of Z_c. Moreover, comparative studies are made with five group contribution methods. It is also demonstrated that by employing the Peng-Robinson EOS, and without prior knowledge of the critical properties, it is possible to calculate various thermophysical properties including P^sat., T_b, , ∆H^vap. , C_p, and even the T_c and P_c themselves.     

High strain electromechanical actuators based on electrodeposited polypyrrole doped with di-(2-ethylhexyl)sulfosuccinate

The low-voltage electromechanical actuation of polypyrrole (PPy) doped with di-(2-ethylhexyl)sulfosuccinate (DEHS) has been investigated. The PPy-DEHS has been prepared both chemically (cast as films from solution) and by more conventional electrochemical polymerization. Very large strains of ∼30% were obtained during slow-scan redox cycling of the electrochemically prepared PPy-DEHS films. In constrast, PPy-DEHS films cast from solutions of the chemically polymerized polymer gave actuation strains of ∼2.5%. The polymerization method was also found to have a significant effect on the structure, conductivity and mechanical properties of the PPy-DEHS materials. The conductivity of the electrochemically polymerized PPy-DEHS was 75 S cm⁻¹, considerably higher than that found for the chemically derived polymer (7 S cm⁻¹). The structure of the PPy-DEHS was further elucidated from UV-vis, Raman and FT-IR spectral studies which indicated that the conjugation length of the PPy could be increased significantly by varying the polymerization method. Films obtained by casting chemically prepared PPy-DEHS showed higher modulus (2.3 GPa) than electropolymerized PPy-DEHS (0.6 GPa), but were more brittle. Both materials were electroactive in acetonitrile/water electrolyte. The higher actuation strain observed in the electrochemically prepared films was attributed to a more open molecular structure (as indicated by the lower modulus) allowing for easier ion diffusion and a higher conductivity allowing easier charge transfer.     

An adaptive learning automata-based ranking function discovery algorithm

Due to the massive amount of heterogeneous information on the web, insufficient and vague user queries, and use of the same query by different users for different aims, the information retrieval process deals with a huge amount of uncertainty and doubt. Under such circumstances, designing an efficient retrieval function and ranking algorithm by which the most relevant results are provided is of the greatest importance. In this paper, a learning automata-based ranking function discovery algorithm in which different sources of information are combined is proposed. In this method, the learning automaton is used to adjust the portion of the final ranking that is assigned to each source of evidence based on the user feedback. All sources of information are first given the same importance. The proportion of a given source increases, if the documents provided by this source are reviewed by the user and decreases otherwise. As the proposed algorithm proceeds, the probability of appearance of each source in the final ranking gets proportional to its relevance to the user queries. Several simulation experiments are conducted on well-known data collections and query types to show the performance of the proposed algorithm. The obtained results demonstrate that the proposed algorithm outperforms several existing methods in terms of precision at position n, mean average precision, and normalized discount cumulative gain.     

Transmission pricing and recovery of investment costs in the deregulated power system based on optimal circuit prices

Transmission pricing has become a major issue in the discussions about the deregulated electricity markets.Consequently,open access to the transmission system is one of the basic topics to allow competition among participants in the energy market.Transmission costs have an important impact on relative competition among participants in the energy market as well as on short-and long-term economic efficiencies of the whole electricity industry,although they represent only close to 10% of the energy market price.This paper deals with the design and tests of a transmission pricing method based on the optimal circuit prices derived from the economically adapted network(EAN).Prices derived from the EAN have the advantage of being in tune with the maximum revenue allowed to the owner of transmission assets and simplifying the optimal allocation of transmission costs among participants.Beginning from the conceptual design,the proposed method is tested on a three-bus network and on the IEEE 24-bus reliability test system.     

A new rateless code with unequal error protection property

In our previous work, “robust transmission of scalable video stream using modified LT codes”, an LT code with unequal packet protection property was proposed. It was seen that applying the proposed code to any importance-sorted input data, could increase the probability of early decoding of the most important parts when enough number of encoded symbols is available at the decoder’s side. In this work, the performance of the proposed method is assessed in general case for a wide range of loss rate, even when there are not enough encoded symbols at the decoder’s side. Also in this work the degree distribution of input nodes is investigated in more detail. It is illustrated that sorting input nodes in encoding graph, as what we have done in our work, has superior advantage in comparison with unequal input node selection method that is used in traditional rateless code with unequal error protection property.     

Polyphenol-rich seaweed (Eucheuma cottonii) extract suppresses breast tumour via hormone modulation and apoptosis induction

The edible red seaweed Eucheuma cottonii is abundantly cultivated for carrageenan production. This study investigated the effects of dietary E. cottonii polyphenol-rich extract (ECME) on breast cancer. In vitro assays showed that ECME was antiproliferative against oestrogen-dependent MCF-7 and oestrogen-independent MB-MDA-231 human breast-cancer cells (IC₅₀ values of 20 and 42 μg/ml, respectively) but was non-toxic to normal cell lines. The ECME (150 and 300 mg/kg BW) was fed to female rats and, after 4 weeks, rat mammary tumour was induced using LA7 cells (inoculated subcutaneously). The ECME inhibited tumour development and erythrocyte lipid peroxidation in the cancer-induced rats, dose-dependently. It showed anti-oestrogenic effects on the rat estrous cycle and serum hormone levels. Electron microscopy and histopathology observations confirmed apoptosis in the rat mammary tumours. The polyphenol-rich ECME was tumour-suppressive via apoptosis induction, downregulating the endogenous oestrogen biosynthesis, and improving antioxidative status in the rats.     

A low‐power,area‐efficient multichannel receiver for micro MRI

A new integrated, low‐noise, low‐power, and area‐efficient multichannel receiver for magnetic resonance imaging (MRI) is described. The proposed receiver presents an alternative technique to overcome the use of multiple receiver front‐ends in parallel MRI. The receiver consists of three main stages: low‐noise pre‐amplifier, quadrature down‐converter, and a band pass filter (BPF). These components are used to receive the nuclear magnetic resonance signals from a 3 × 3 array of micro coils. These signals are combined using frequency domain multiplexing (FDM) method in the pre‐amplifier and BPF stages, then amplified and filtered to remove any out‐of‐band noise before providing it to an analog‐to‐digital converter at the low intermediate frequency stage. The receiver is designed using a 90 nm CMOS technology to operate at the main B₀ magnetic field of 9.4 T, which corresponds to 400 MHz. The receiver has an input referred noise voltage of 1.1 nV/√Hz, a total voltage gain of 87 dB, a power consumption of 69 mA from a 1 V supply voltage, and an area of 305 µm × 530 µm including the reference current and bias voltage circuits. Copyright © 2013 John Wiley & Sons, Ltd.