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[en] The international oil market faced volatile conditions due to regional political factors, namely, the Iraqi invasion of Kuwait in August 1990. Political events were the major driving force of the industry in the early 1990s. The situation in the Gulf region has quieted considerably since March 1991 and, in response, the oil market and particularly crude oil prices have settled to their prewar range. The Organization of the Petroleum Exporting Countries (OPEC) has attempted once again to exert its influence by regulating the crude oil market through supply management in its postwar meetings. The organization is faced with a number of challenges both in the short and long run in stabilizing crude oil prices. While in the short run the concern is how to prevent crude oil prices from dopping, in the long term the challenge is building adequate production and export capabilities for the future. 3 figs., 4 tabs
Journal
[en] The magnetic stability and electronic properties of the FeO compound are investigated using the framework of an all-electron full-potential linearized augmented-plane wave (FP-LAPW) method within the generalized gradient (GGA) and GGA+U approximations. We locate the ground state to be of rhombohedrally distorted B1 structure with compression along [111] direction. The values for the band gap and magnetic moments obtained with this parameter-free first principles method are in good agreement with experimental data. Finally, we conclude that the treatment of the correlated electrons (GGA+U) approach with the inclusion of spin-orbit-coupling (SOC) is important for the correct description of this compound.
Journal
Physics of the Solid State; ISSN 1063-7834; 
; v. 62(3); p. 472-479
; v. 62(3); p. 472-479
[en] In the present work, a typical combined cooling, heating and power (CCHP) system comprised of boiler, flat solar collectors, absorption chiller and heat storage tank was investigated. The described system was considered to supply the given electricity, cooling and heating demand of a residential building; with heating and cooling needs of 100 and 50 kW, respectively. To find the optimum hybrid configurations with high reliability, low costs, low fuel consumption and emissions, a computer program was provided by authors in FORTRAN language. Different fuel prices were considered in the present work. The results indicated that the optimal operation strategy changes with Boiler and NGG fuel prices while it also changes with increasing the number of solar collectors, heat storage capacity and consequently decreasing total annual emission.
Journal
Journal of Mechanical Science and Technology (Online); ISSN 1976-3824; ; v. 28(5); p. 2003-2014
; v. 28(5); p. 2003-2014
[en] The EUSO experiment is currently under study by ESA for a possible installation on the International Space Station. The experiment is designed to study, by means of a space-based observational apparatus, the Extensive Air Showers produced in the atmosphere by Extreme High-Energy Cosmic Rays. The design of a fast, single-photon sensitive photo-detector in the near UV, covering a large area with a few hundreds thousands pixels, and suitable for 3 years of operation in space is a challenging task. The basic aspects of the current EUSO photo-detector design, based on the presently known requirements and constraints, and the results of the preliminary studies carried on so far will be described
Journal
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment; ISSN 0168-9002; ; CODEN NIMAER; v. 504(1-3); p. 99-102
; CODEN NIMAER; v. 504(1-3); p. 99-102
[en] Through using spin coating technique, Cu2CdSnS4 (CCTS) quaternary alloy nanostructures were successfully deposited on GaN substrate using a wide range of spin coating speeds; 1500, 2000, 2500, 3000 and 3500 RPM at annealing temperature 300 °C. The optical properties were investigated through UV–vis which revealed the changing of energy band gap as the spin coating speed increases, in addition, to verify specific models of refractive index and optical dielectric constant. The structural properties were studied by X-ray diffraction which indicated that the number and intensity of the peaks were changed as the spin coating speed changes. The morphological and topographical studies of CCTS were elaborated by field emission-scanning electron microscopy and atomic force microscopy. The obtained results suggest that CCTS nanostructures deposited on GaN substrate are very suitable for optoelectronic applications, that are in accordance with the available theoretical and experimental data. (author)
Journal
Indian Journal of Physics (Online); ISSN 0974-9845; ; v. 92(6); p. 695-703
; v. 92(6); p. 695-703
[en] We present the results of first-principles study of the structural and electronic properties of Bex Zn1-xS and Be x Zn 1-xTe alloys for different concentrations x. The computational method is based on the full-potential Muffin-Tin orbitals method (FP-LMTO) in the framework of density-functional theory (DFT). The exchange and correlation energy is described in the local density approximation (LDA) using Perdew-Wang parameterization. We have investigated the effect of composition on the ground-state properties, band gap and effective mass. We report the results concerning the variation of the gaps and crossover of the direct, indirect bandgap and the bowing. Using the approach of Zunger and coworkers, the microscopic origins of bandgap bowing have been detailed and explained. A reasonable agreement is found from the comparison of our results with other theoretical calculations. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Journal
[en] We have investigated the structural properties of seven different structure types of Mg2Si which include the cubic CaF2, orthorhombic PbCl2, hexagonal Ni2In, tetragonal Al2Cu, Laves phase (cubic MgCu2), hexagonal MgZn2 and dihexagonal MgNi2 type of structures, using a full potential linearized augmented plane wave method as implemented in WIEN2k within the framework of density functional theory. The exchange-correlation potential is treated by the new form of generalized gradient approximation (GGA-PBEsol). In total energy calculations it is clearly seen that cubic CaF2-type structure is stable at ambient conditions, and it undergoes a first-order phase transition to orthorhombic PbCl2-type, then to the hexagonal Ni2In-type structure and finally to the cubic Laves phase MgCu2-type. A new structure type is predicted to be stable at high pressure. Moreover, we intend to combine the electronic structure calculations performed by mean of generalized gradient approximation and modified Becke-Johnson potential with Boltzmann transport theory as incorporated in BoltzTraP code to interpret and predict the thermoelectric performance of each stable phase as a function of the chemical potential at various temperatures. We find a high thermoelectric thermopower values in cubic CaF2-type structure that could promise an excellent candidate for potential thermoelectric applications. (author)
Journal
Indian Journal of Physics (Online); ISSN 0974-9845; ; v. 90(12); p. 1403-1415
; v. 90(12); p. 1403-1415
[en] We have performed ab-initio self-consistent calculations on the full-potential linear muffin-tin orbital method with the local-density approximation and local spin-density approximation to investigate the structural and electronic properties of EuS and EuSe in its stable (NaCl-B1) and high-pressure phases. The magnetic phase stability was determined from the total energy calculations for both the nonmagnetic (NM) and magnetic (M) phases. These theoretical calculations clearly indicate that both at ambient and high pressures, the magnetic phase is more stable than the nonmagnetic phase. The transition pressure at which these compounds undergo the structural phase transition from NaCl-B1 to CsCl-B2 phase is calculated. The elastic constants at equilibrium in both NaCl-B1 and CsCl-B2 structures are also determined. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Journal
[en] A sensing plate of extended Cu_2Zn_1_-_xCd_xSnS_4 quinternary alloy nanostructures, fabricated on an oxidized silicon substrate by the sol-gel method, is reported in this paper. The fabricated device was characterized and analyzed via field emission-scanning electron microscopy, X-ray diffraction (XRD), and photoluminescence (PL). The XRD peaks shifted towards the lower angle side alongside increasing concentration of cadmium. The average diameter of the Cu_2Zn_1_-_xCd_xSnS_4 quinternary alloy nanostructures falls between 21.55 and 43.12 nm, while the shift of the PL bandgap was from 1.81 eV (x = 0) to 1.72 eV (x = 1). The resulting Cu_2Zn_1_-_xCd_xSnS_4 quinternary alloy nanostructures components were functionalized with oligonucleotides probe DNA molecules and interacted with the target, exhibiting good sensing capabilities due to its large surface-to-volume ratio. The fabrication, immobilization, and hybridization processes were analyzed via representative current-voltage (I-V) plots. Its electrical profile shows that the device is capable to distinguish biomolecules. Its high performance was evident from the linear relationship between the probe DNA from cervical cancer and the target DNA, showing its applicability for medical applications. (orig.)
Journal
Applied Physics. A, Materials Science and Processing; ISSN 0947-8396; ; CODEN APAMFC; v. 123(3); p. 1-9
; CODEN APAMFC; v. 123(3); p. 1-9
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