A REVIEW OF NON-CONVENTIONAL METHODS FOR THE DESULFURIZATION OF RESIDUAL FUEL OIL

Sulfur removal from residual fuel oil has received increasing attention in recent years mainly for the preparation of clean feedstocks for downstream conversion units and to meet the new specifications for petroleum products. This review presents discussion of non-conventional methods of fuel oil desulfurization other than hydrodesulfurization (HDS). These methods include oxidation, electrochemical, sodium, alkali, chemical treatment, and biodesulfurization.     

Design tradeoff analysis of floating-point adders in FPGAs

With gate counts of ten million, field-programmable gate arrays (FPGAs) are becoming suitable for floating-point computations. Addition is the most complex operation in a floating-point unit and can cause major delay while requiring a significant area. Over the years, the VLSI community has developed many floating-point adder algorithms aimed primarily at reducing the overall latency. An efficient design of the floating-point adder offers major area and performance improvements for FPGAs. Given recent advances in FPGA architecture and area density, latency has become the main focus in attempts to improve performance. This paper studies the implementation of standard; leading-one predictor (LOP); and far and close datapath (2-path) floating-point addition algorithms in FPGAs. Each algorithm has complex sub-operations which contribute significantly to the overall latency of the design. Each of the sub-operations is researched for different implementations and is then synthesized onto a Xilinx Virtex-II Pro FPGA device. Standard and LOP algorithms are also pipelined into five stages and compared with the Xilinx IP. According to the results, the standard algorithm is the best implementation with respect to area, but has a large overall latency of 27.059 ns while occupying 541 slices. The LOP algorithm reduces latency by 6.5% at the cost of a 38% increase in area compared to the standard algorithm. The 2-path implementation shows a 19% reduction in latency with an added expense of 88% in area compared to the standard algorithm. The five-stage standard pipeline implementation shows a 6.4% improvement in clock speed compared to the Xilinx IP with a 23% smaller area requirement. The five-stage pipelined LOP implementation shows a 22% improvement in clock speed compared to the Xilinx IP at a cost of 15% more area.     

STRUCTURAL CHARACTERIZATION OF ARABIAN HEAVY CRUDE OIL RESIDUE

The residue (370°C+) from Arabian Heavy Crude Oil was separated into four fractions, asphaltenes, resins, aromatcis and saturates. The four fractions were found to be free of artifacts and analytically significant in themselves. Each fraction was further characterized by elemental analysis, infrared spectroscopy, n.m.r. spectroscopy and mass spectroscopy. The aromatics are the major constituent of the residue and the ratio of asphaltenes, resins, aromatics and saturates is about 2:3:8:3. The strucutral characterization study led to the conclusion that asphaltene fraction is maximum hydrogen deficient followed by resins, aromatics and saturates thus suggesting larger degree of ring condensation in the structure of asphaltenes than resins and aromatics.     

Automated Average Areal Rainfall Calculation inLibya

An automated computer program isdeveloped for calculating areal average rainfall(AAR) value and its implementation is presentedfor the arid region representative country,Libya.The procedure is conceptually simple byconsideration of almost equilateral trianglesconnecting adjacent meteorological stations withthe assumption of linear rainfall change betweenstations. The applications of the methodologyhave been achieved for monthly, seasonal andannual rainfall amounts recorded at 29meteorological stations scattered over thenorthern part of Libya.It has been shown thatthe proposed methodology yields results that arecomparable with the commonly used AAR calculationmethods.     

Prediction of oxide scale growth in superheater and reheater tubes

In this paper a procedure on how to estimate the oxide scale growth in superheater and reheater tube utilizing the empirical formulae and the finite element modeling is proposed. An iterative procedure consisting of empirical formulae and numerical simulation is used to determine scale thickness as both temperature and time increase. Results of the scale thickness over period of time for two different design temperatures of the steam and different heat transfer parameters are presented. The procedures may provide better estimation on the oxide scale growth, provided that all the heat transfer parameters are well specified.     

The Tricriteria Two-Machine Flowshop Scheduling Problem

The literature on the two-machine flowshop scheduling problem reveals that the problem has been addressed with bicriteria of either makespan and mean flowtime or makespan and maximum tardiness (lateness). This paper extends the problem to all the three criteria (tricriteria) where the objective is to minimize a weighted sum of makespan, mean flowtime, and maximum lateness. A dominance relation and a lower bound are established. The dominance relation and the lower bound are used to develop a branch-and-bound algorithm. The dominance relation is also used to develop several heuristics. An extensive computational analysis is conducted to evaluate the performance of the dominance relation and the heuristics. The analysis shows that the dominance relation is effective. The analysis also shows that the heuristics are quite efficient, and some heuristics have an error of less than 1%. Moreover, these heuristics have the desirable property that the error does not increase by the number of jobs.     

Third-order accurate finite volume schemes for Euler computations on curvilinear meshes

After looking for a convenient definition of accuracy for finite-volume schemes on structured meshes, a high-order accurate scheme is constructed for the Euler equations. Thanks to suitably weighted discretization operators, the proposed scheme is third-order on mildly deformed grids and second-order on highly deformed grids. The influence of mesh deformations on the scheme accuracy is studied theoretically and numerically. Numerical results are shown for a Lamb vortex, subsonic flow past a cylinder and transonic flow past a NACA0012 airfoil.     

Fatty acids stimulate trehalose synthesis in trophocytes of the cockroach (Periplaneta americana) fat body

Trophocytes from the disaggregated fat body of the cockroach (Periplaneta americana) respond to synthetic hypertrehalosemic hormone (HTH) by increasing the rate of trehalose synthesis. The cells give a similar response when incubated with stearic, oleic, linoleic, or arachidonic acid. A maximal increase in trehalose synthesis was obtained with 1-10 microM fatty acids. Synthesis of trehalose by the trophocytes was also increased by 1 microM prostaglandin F2alpha to nearly the same extent as that evoked by HTH. Furthermore, the data show that the trophocytes are capable of converting linoleic acid into arachidonic acid. This suggests that the cells may convert arachidonic acid, formed from the linoleic acid released by the action of HTH, to a prostaglandin which serves as an integral part of the hypertrehalosemic mechanism.