Determination of best possible correlation for gas compressibility factor to accurately predict the initial gas reserves in gas-hydrocarbon reservoirs

Gas compressibility factor or z-factor plays an important role in many engineering applications related to oil and gas exploration and production, such as gas production, gas metering, pipeline design, estimation of gas initially in place (GIIP), and ultimate recovery (UR) of gas from a reservoir. There are many z-factor correlations which are either derived from Equation of State or empirically based on certain observation through regression analysis. However, the results of the z-factor obtained from different correlations have high level of variance for the same gas sample under the same pressure and temperature. It is quite challenging to determine the most accurate correlation which provides accurate estimate for a range of pressures, temperatures, and gas compositions. This paper presents a novel method to accurately estimate GIIP of an Australian tight gas field through identification of the most appropriate z-factor correlations, which can accurately determine the z-factor and other PVT properties for a wide range of gas compositions, temperatures, and pressures. The sensitivity study results demonstrated that a single correlation cannot work across the range of pressures and temperatures for a certain gas sample necessary to calculate z-factor during simulation process and/or other analysis, such as material balance and volumetric estimate.     

Integration of GIS and multicriteria decision analysis for urban aquaculture development in Bangladesh

Site selection is a key factor in any aquaculture operation, affecting both success and sustainability as well as solving land or water use conflicts. This study was conducted to identify suitable sites for carp farming development in urban water bodies (UWBs) of Chittagong, Bangladesh using Geographical Information Systems (GIS) based MultiCriteria Evaluation (MCE) of water, soil and infrastructure database. ASTER imagery and 14 thematic layers were analyzed with ENVI and GIS capabilities, and developed a series of GIS models to identify and prioritize the appropriate UWBs for carp farming. The study identified 487 UWBs occupying 362 ha and revealed 280 ha (77%) is the most suitable, 36 ha (10%) is moderately suitable and 46 ha (13%) is not suitable which was consistent with field verification. The results are encouraging for extension of carp culture and diversify the economic activities of the urban dwellers.     

Improved calculation of Si sputter yield via first principles derived interatomic potential

Silicon sputter yield under medium energy Ar+ ion bombardment is calculated via molecular dynamics, using a highly accurate interatomic potential for Ar-Si interactions derived from first-principles calculations. Unlike the widely used universal repulsive potentials such as the Moliere or ZBL parameterizations, this new potential, referred to as DFT-ArSi, is developed via localized basis density functional theory. Sputter yields for Si obtained with the DFT-ArSi potential at 500 eV and 1 keV incident energies are found to be within 6% and 2% of experimental results, respectively, while errors using existing potentials are typically on the order of 11%. The DFT-ArSi potential differs from existing empirical potentials in the ∼1 Å interatomic separation range which is shown to be the most important range for modeling low-to-medium energy ion bombardment.     

Aloe vera gel: a new thickening agent for pigment printing

An attempt was made to print cotton fabric with pigments using a new thickening agent based on Aloe vera gel in combination with sodium alginate. The results were compared with the standard conventional printing recipe containing synthetic thickener, and a favourable effect of Aloe vera introduction was achieved. The results show that the properties of the printed fabric (sharpness, colour yield, overall fastness properties, softness, and water vapour transmission) are dependent on the percentage of Aloe vera gel in the thickener combination, the concentration of printing auxiliaries, and the curing conditions. Optimal printing properties were achieved by using a printing paste containing 80% Aloe vera/20% sodium alginate (700 g kg^?1), pigment (50 g kg^?1), binder (145 g kg^?1), fixer (10 g kg^?1), and ammonium sulfate (5 g kg^?1), followed by drying at 85 °C for 5 min and curing at 150 °C for 3 min. The sample printed with the new recipe showed superior rubbing fastness and handle properties, with a slightly lower colour yield, when compared with the sample printed with synthetic thickener. Finally, economic issues arising from synthetic thickener substitution are highlighted.     

Effect of different titania phases on the hydrogen gas sensing features of polyaniline/TiO2 nanocomposite

This paper presents a resistance-based hydrogen gas sensor using polyaniline (emeraldine)/TiO₂ nanocomposite (PT–NC) thin film. It is demonstrated that different gas sensing features can arise when various TiO₂ phases (anatase and rutile) are applied. The different wt% of TiO₂ phases were dispersed into an acidic solution of aniline monomers and PT–NCs were synthesized by an in-situ self-assembly chemical oxidative polymerization method of aniline. PT–NCs deposited on an epoxy glass substrate having Cu-interdigited electrodes for hydrogen gas sensing at air pressure and room temperature. Our results show that the better sensitivity of the sensor strongly depends on the sensor surface morphology and its components. Furthermore, hydrogen gas sensing mechanism of the sensor based contact areas between Pani chains and TiO₂ grains was studied.     

Synthesis,Characterization and Catalytic Activities of Palladium(II) Nitroaryl Complexes

Two palladium(II) nitroaryl complexes trans-[bromo(p-nitrophenyl)bis(triphenylphosphine)palladium(II)] 1 and trans-[bromo(2,4-dinitrophenyl)bis(triphenylphosphine)palladium(II)] 2 have been synthesized. The complexes were characterized by FTIR and NMR (¹H, ¹³C and ³¹P) spectroscopy and elemental analysis. The molecular structure of complex 2, as confirmed by X-ray crystallography, reveals that the Pd atom and its neighboring groups (two PPh₃, Br and phenylene group) lie in a slightly distorted square plane. In the UV–Vis spectra of the complexes 1 and 2, the palladium to aryl charge transfer bands were observed. The emission peaks from the singlet excited states (S₁ → S₀) were observed in the photoluminescence spectra of the complexes. The thermal stability of the complexes has been studied by thermal gravimetric analysis (TGA). TGA data showed that both complexes are thermally stable up to 200 °C, and complex 1 is more stable than 2. The catalytic efficiency of the new palladium(II) complexes was studied as demonstrated using the Sonogashira coupling reactions with good yields. The experimental results suggest that the Sonogashira coupling reactions can be performed at moderate temperature (50 °C) using these new palladium(II) complexes as catalysts.     

Effect of multipath fading and multiple access interference on broadband code division multiple access systems

In this paper, the performance of uncoded uplink transmissions in a broadband code division multiple access (CDMA) system using tapped delay line (TDL) antenna array under multipath conditions is investigated. An expression for broadband CDMA system is derived to calculate the optimal weights of TDL antenna array. Using the derived broadband expression, the performance of TDL antenna array is investigated and compared with that of the already existing narrowband systems. Simulation results show that TDL antenna array can reduce multipath fading and multiple access interference (MAI). It is shown that if the signal‐to‐noise ratio (SNR) level is maintained at 20 dB and two‐ray channel model is used, two antennas with four taps each can support 30 users with a BER of 10^?3. If three‐ray channel model is used, the same antenna arrangement is not enough to support 30 users. To support these 30 users with BER of 10^?3, the number of taps needs to be increased to eight. Finally, the number of taps needs to be further increased to 16 if four‐ray channel model is used. Not only that, the SNR should also be increased to 25 dB to achieve the same BER. Copyright © 2011 John Wiley & Sons, Ltd.     

Network coding for unicast in a WiFi hotspot: Promises,challenges, and testbed implementation

In offices and residential buildings, WiFi networks have become a primary means for providing Internet access to wireless devices whose dominant traffic pattern is unicast. In the meantime, the emergence of network coding has brought about great promises for multicast in communication networks where intermediate nodes are allowed to process independent incoming information flows. Little is known about network coding for unicast, however. The objective of this paper is thus to depart from multicast scenarios and shed light on several possible unicast scenarios to which network coding may be applied in a WiFi hotspot in order to obtain communication benefits such as throughput gain, fairness, and reduced protocol complexity. We identify five representative scenarios in which network coding may be used to benefit unicasting in a WiFi hotspot. Several open research issues and practical challenges related to each scenario are discussed individually. To illustrate the benefits of network coding for unicast in a WiFi hotspot, we propose and implement iCORE: The interface COoperation Repeater-aided network coding Engine. iCORE is a practical system in which multi-channel multi-radio repeaters are used to relay unicast traffic for those terminals sitting far away from an access point and suffering from weak signals at a WiFi hotspot. It is based on our last scenario which illustrates the synergy among network coding, opportunistic routing, and interface management. Utilizing idle wireless interfaces and listening to traffic opportunistically, iCORE allows packets to move across the interfaces and to be coded across flows whenever it sees more transmission opportunities. We evaluate iCORE on a four-node chain-like topology testbed implemented using IEEE 802.11b/g radios and compare it to MORE – the state-of-art intra-flow network coding implementation based on opportunistic routing. Our experimental results reveal promising gains in terms of throughput over MORE.