Enhanced mobility and environmental stability in all organic field‐effect transistors: The role of high dipole moment solvent

Low‐operating voltage, high mobility, and stable organic field‐effect transistors (OFETs) using polymeric dielectrics such as pristine poly(4‐vinyl phenol) (PVP) and poly(methyl methacrylate) (PMMA), dissolved in solvents of high dipole moment, have been achieved. High dipole moment solvents such as propylene carbonate and dimethyl sulfoxide used for dissolving the polymer dielectric enhance the charge carrier mobilities by three orders of magnitude in pentacene OFETs compared with low dipole moment solvents. Fast switching circuits with patterned gate PVP‐based pentacene OFETs demonstrated a switching frequency of 75 kHz at input voltages of |5 V|. The frequency response of the OFETs is attributed to a high degree of dipolar‐order in dielectric films obtained from high‐polarity solvents and the resulting energetically ordered landscape for transport. Remarkably, these pentacene‐based OFETs exhibited high stability under bias stress and in air with negligible shifts in the threshold voltage. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1533–1542     

Ultrasound Promoted and Ionic Liquid Catalyzed Cyclocondensation Reaction for the Synthesis of 4(3H)-Quinazolinones

4(3H)‐Quinazolinones were synthesized in high yields by one‐pot three‐component condensation of anthranilic acid, carboxylic acid and aniline in the presence of ionic liquid such as 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF₄) as catalyst under solvent free and neutral conditions.     

Brans-Dicke Cosmology–A Generalization in Anisotropic Space-Time Models

The generalized Brans-Dicke (BD) Cosmology has been studied for Bianchi-I, Bianchi-III and Kantowski-Sachs anisotropic space-time models. Solutions have been obtained for radiation-dominated era, stiff matter epoch and other equations of state.     

Cavitation--a novel technique for making stable nano-suspensions

The purpose of the present study was to obtain nano-scale particles of styrene butadiene rubber. As SBR particles are elastic in nature, conventional methods of size reductions such as impacting, grinding are unable to achieve the final size. So, attempts have been made here to make the nano-particles of the SBR using cavitation technique. Both acoustic and hydrodynamic cavitation techniques have been employed and studied. Hydrodynamic cavitation has been proved to be more energy efficient than the acoustic cavitation on the basis of various parameters. The maximum production rate equivalent to 2 kg/h (solid processing) has been achieved in the newly developed hydrodynamic cavitation set-up (made in house). Similar to transient cavitation, stable cavitation has also been shown to contribute for reduction in the size of the material with very low variation in size. This technique has been proved successful for the size-reduction of the elastic material to nano-scale, thus it may also be used for the size-reduction of the other brittle and hard material by adjusting various cavitational parameters.     

A steam-soak production model for thick gravity drainage petroleum reservoirs

Summary This paper deals with the production performance for the steam-soak process as applied to a reservoir where oil is produced by gravity drainage. An improved analytical temperature profile which is simple, less time consuming and comparable to the exact solution is used to compute the viscosity variation inside the reservoir. Based on this temperature profile the continuity equation is solved by finite difference technique to find the oil height as a function of radius and time which in turn gives the flow rate and cumulative oil production. Comparison of the developed model with available field data shows that the model gives better prediction of steam-soak oil recovery than other comparable methods.

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Ein Modell zur Ausbeute von Rohölfeldern durch Schwerkraftsickerung bei zyklischer Dampfinjektion

Übersicht Behandelt wird das Förderverhalten eines Rohölspeichers bei Dampfinjektion und Schwerkraftsickerströmung. Zur Berechnung der Viskositätsverteilung im Reservoir wird ein vereinfachtes Temperaturfeld, welches das wahre annähert, benutzt. Mit dieser Temperaturverteilung wird die Kontinuitätsgleichung nach der Finite-Differenzen-Methode gelöst und die Ölstandshöhe als Funktion von Radius und Zeit bestimmt. Daraus ergibt sich der Volumenstrom und die kumulierte Fördermenge. Ein Vergleich des hier entwickelten Modells mit Daten eines Ölfeldes zeigt, daß es bessere Vorhersagen liefert als vergleichbare Methoden.

     

Visualization of water and surfactant floods in oil-saturated porous media

The flow of water and 1% surfactant solution displacing oil through homogeneous and non-homogeneous porous media have been studied experimentally. The results are shown by taking the photographs of unstable interface at regular interval of time. These photographs suggest that the spreading of the moving interface in lateral direction is more for 1% surfactant solution displacing oil than for water displacing oil and also the interface is more stable for surfactant flooding in the bed. The wavelengths of viscous fingers measured from the experiments are found to be in good agreement with the theoretical predictions for homogeneous bed. The percentage oil recovery at breakthrough is improved considerably with the use of surfactant solution. Effect of flow rate on recovery and breakthrough time has also been studied. Finally, the effect of non-homogeneous packing on the growth of fingers has been studied by creating non-homogeneous medium in an otherwise homogeneous porous medium.     

Stability of miscible fluid displacement in a porous medium

Summary The stability of miscible fluid displacement through porous media has been investigated when concentration induced density and viscosity gradients are present. The dependence of Rayleigh's number on the horizontal planform of cellular motion is established and it is shown that the Rayleigh and wave numbers interact in a nonlinear fashion and hence have to be treated as two independent parameters in the analysis of stability process.Übersicht Untersucht wird die Stabilität der Bewegung mischbarer Flüssigkeiten durch ein poröses Medium bei konzentrationsbedingten Dichte- und Viskositätsgradienten. Der Zusammenhang zwischen der Rayleigh-Zahl und der horizontalen Planheit der Zellbewegung wird aufgezeigt und nachgewiesen, daß die Rayleigh-und Wellenzahlen sich nichtlinear beeinflussen und folglich als zwei unabhängige Parameter der Stabilitäts-analyse zu betrachten sind.

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Stabilität der verschiebung mischbarer flüssigkeiten in einem porösen medium

     

Anchoring Mechanism of ZnO Nanoparticles on Graphitic Carbon Nanofiber Surfaces through a Modified Co‐Precipitation Method to Improve Interfacial Contact and Photocatalytic Performance

A facile three‐step co‐precipitation method is developed to synthesize graphitic carbon nanofibers (CNFs) decorated with ZnO nanoparticles (NPs). By interchanging intermediate steps of the reaction processes, two kinds of nanohybrids are fabricated with stark morphological and physicochemical differences. The morphologies differ because of the different chemical environments of the NP/nanocluster formation. The hybrid with larger and non‐uniform ZnO nanocluster size is formed in liquid phase and resulted in considerable interfacial defects that deteriorate the charge‐transfer properties. The hybrid with smaller and uniform ZnO NPs was formed in a dry solid phase and produced near‐defect‐free interfaces, leading to efficient charge transfer for superior photocatalytic performance. The results broaden the understanding of the anchoring/bonding mechanism in ZnO/CNF hybrid formation and may facilitate further development of more effective exfoliation strategies for the preparation of high‐performance composites/hybrids.