Electrical and structural properties of polyaniline/cellulose triacetate blend films

Polyaniline (PANI) has been blended with cellulose triacetate (CTA) to obtain both good mechanical properties and good electrical properties. The effects of PANI weight percentage on the optical, structural, morphological and electrical properties in the blend films of polyaniline and cellulose triacetate (PANI/CTA) have been investigated. The phenomenon of percolation was observed in these blend films. It is found that the electrical conductivity of the blend films increases with the increase of polyaniline content up to a value of 10⁻⁴ S cm⁻¹ at 84 weight percentage of PANI. The experimental percolation threshold of the dried blend films is obtained at 9.5 wt% of polyaniline. The values of Mott’s temperature, density of states at the Fermi level [N (E _f)], hopping distance (R _hop), and barrier height (W _hop) for PANI/CTA blend films are calculated. By applying Mott’s theory, it is found that the PANI/CTA blend films obey the three dimensional variable range hopping mechanism.     

Optimal solar array configuration and DC motor field parameters formaximum annual output mechanical energy

A procedure is presented for the proper design of systems comprising photovoltaic solar generators directly supplying DC motors. The method is based on maximizing the total annual gross mechanical energy delivered to a mechanical load with a given torque-speed characteristic. The seasonal variations of both the isolation level and the ambient temperature are taken into account. The proposed technique is applied to two practical case studies, and the resulting optimal design parameters are compared with those available in the literature. A comparison is also made between the optimal separately excited and series motor design alternatives regarding the annual gross mechanical output energy     

A Cross Layer Scheduling Framework for Supporting Bursty Data Applications in WCDMA Networks

In future wireless networks multimedia applications are expected to finally dominate the overall traffic volume. Shared channels are more suitable for the transmission of this type of traffic, as they are able to periodically adjust their transmission rate. In this paper, we introduce a cross-layer framework for WCDMA based networks which aims to make the packet scheduling procedure more efficient. In addition to that, we further propose a traffic scheduling scheme which serves the connections not only according to their delay sensitivity, but also according to the predicted state of their wireless channel. The efficiency of the proposed scheme, in terms of average packet delay and channel utilization is verified via simulations.     

Model tree approach for predicting uniaxial compressive strength and Young’s modulus of carbonate rocks

Bulletin of Engineering Geology and the Environment - The uniaxial compressive strength (UCS) and Young’s modulus (E) of rock are important parameters for evaluating the strength,...     

A Contribution to the Frequency Analysis and Transient Response of Power Transformer Windings

Abstract—This article proposes a new approach to study the frequency response and the transient analysis of power transformer windings. For improved accuracy, the suggested model includes, among other equivalent circuit elements, the mutual magnetic couplings between any winding turn and all others. This implies that the equivalent inductance of any considered turn will be a location-dependent parameter. Accordingly, the winding will be analyzed as a non-uniform transmission line. Through the application of a recursive circuit reduction technique, a closed-form Laplace s-domain analytical expression for the winding's input impedance can be obtained for any neutral treatment. The resulting expression can be used to determine the winding's series and parallel resonance frequencies. The s-domain expression for the input impedance, in connection with the numerical inverse Laplace transform, will be utilized for determination of the winding's time-domain transient response for any input voltage or current time waveform. Accuracy increases with the assumed number of winding sections, which can be even increased to the actual number of turns, limited only by the available computation resources. The results of case studies are in good agreement with those available in the literature using the time-domain solution of the simultaneous differential equations in the state variables.     

Preparation of shish‐kebab and nanofiber polyethylene with chromium/Santa Barbara amorphous silica‐15 catalysts

Cr/SBA‐15 catalysts were prepared by the grafting of chromium nitrate nonahydrate [Cr(NO₃)₃·9H₂O] complexes onto SBA‐15 mesoporous materials. Shish‐kebab and nanofiber polyethylenes (PEs) were prepared under different temperatures via ethylene extrusion polymerization with the Cr(NO₃)₃·9H₂O catalytic system. The diameter of a single nanofiber was 100–250 nm. Scanning electron microscopy images showed that the polymer obtained from the SBA‐15‐supported catalyst under different polymerization temperatures produced nanofiber and/or shish‐kebab morphologies. X‐ray diffraction and differential scanning calorimetry were used to characterize microstructures of the materials. Polymers obtained with all of the catalysts showed a melting temperature, bulk density, and high load melt index; this indicated the formation of linear high‐density PE. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and structure study of copolymers from thiadiazole fused indolocarbazole and dithienosilole

We report synthesis and characterization of two D-A polymers (PSDT-C12 and PSDT-EH) with different side chains. Both polymers are based on alternate 12,13-dioctyl-indolo[2,3-a][1,2,5]thiadiazolo[3,4-c]carbazole (TDZIC) and dithienosilole derivative units in polymer main chain. We used TDZIC to enlarge the 2D conjugated plane of acceptor monomers by fusing benzothiadiazole (BT) unit with an indole unit having alkyl groups. PSDT-C12 exhibited 10 nm redshift compared to PSDT-EH in solid films, while their absorption spectra were almost identical in solutions. Since the backbone and side chains on the indolocarbazole group are the same, the redshift on PSDT-C12 could be resulted from the dodecyl (C12) side chain on the dithienosilole unit and different molecular weight between these two polymers. PSDT-C12 has a larger molecular weight than PSDT-EH. Therefore possibly both side chains and molecular weight contributed to the difference in the absorption spectra in solid films. The straight C-12 side chain has less steric hindrance than the branched EH side chain in solid films. PSDT-C12 has a longer main chain (larger molecule weight) than PSDT-EH, which can favour a more extended main chain interaction. The vibronic peak at 519 nm and shoulder at 563 nm in the PSDT-C12 film further confirmed stronger main chain interaction. Geometry optimization showed that head–tail (HT)-PSDT had a more twisting conjugated backbone with larger dihedral angle between dithienosilole unit and thiadiazole-fused ring compared to head–head/tail–tail (HH/TT)-PSDT.     

A probabilistic model for assessing the reliability of wind farms in a power system

Modeling the generation of a wind farm and its effect on power system reliability is a challenging task, largely due to the random behavior of the output power. In this paper, we propose a new probabilistic model for assessing the reliability of wind farms in a power system at hierarchical level II (HLII), using a Monte Carlo simulation. The proposed model shows the effect of correlation between wind and load on reliability calculation. It can also be used for identifying the priority of various points of the network for installing new wind farms, to promote the reliability of the whole system. A simple grid at hierarchical level I (HLI) and a network in the north-eastern region of Iran are studied. Simulation results showed that the correlation between wind and load significantly affects the reliability.     

A decision-process model of relational risk and governance and their impact on performance

The purpose of this paper is to investigate the link among risk, governance, and performance. In order to achieve this objective, the paper examines the impact of relational risk on governance decision options (trust, bilateral control, and unilateral control) and performance (design time). Survey research was conducted to collect data from 221 new product development (NPD) relationships and structural equation modeling was conducted to test the hypotheses. The results suggest that relational risk influences trust and bilateral control negatively and unilateral control positively. Results also indicated that trust and bilateral control are positively related to shortened design time while unilateral control and shortened design time are negatively related. We also found that there are threshold effects for modes of governance decision as they influence shortened design time. This study enhances the understanding of NPD relationships by examining the key mechanisms through which governance decision modes are influenced and how they influence NPD performance. In summary, this study shows how relational risk perception through affecting governance decision modes influence shortened design time.