Monitoring the Key Components and Elimination of Asphaltenes Precipitation in Crude by a New Alternative Route

The crude composition was determined by distillation on a true boiling point apparatus individually. Then crude naphthas were introduced to a gas chromatograph and asphaltenes were determined by extraction. Quantities of key components were calculated by prescribed mathematical equations. On the basis of relative quantities of key components, 21 blends of 12 crudes were prepared caused asphaltenes precipitation in desalter. Seven blends remained successful, causing no further asphaltenes precipitation, and one of the successful blends was chosen to prepare a batch of 55,000 barrels and was passed through desalter. No further asphaltenes precipitation was found during the whole operation.     

Versatile voltage-mode universal biquad filter using the operational amplifier pole

A new multifunction voltage-mode biquad filter topology having three inputs and one output is described. The filter consists of a single operational amplifier (OA), a single capacitor, and two resistors and supports LP, BP, HP, AP and Notch filtering signals from the same topology, without requiring additional components besides being devoid of component matching constraints. The filter uses OA pole and has thereby acquired suitability for extended frequency operation. The natural angular frequency ω₀ and the Q can be separately tuned. The circuit has low sensitivity figures. PSPICE simulation results are employed to verify the circuit performance.     

Simple first-order translinear-C current-mode all-pass sections

A first-order translinear-C current-mode (CM) all-pass section (APS) using two current-controlled conveyors (CCCII) and a single capacitor is given. A canonical CM-APS using only one dual-output CCCII and one capacitor is also derived from the proposed configuration. The circuits are analysed for the non-idealities of CCCII and possess attractive sensitivity performance. The proposed circuits are electronically tunable over a wide frequency range. RSPICE simulation results for ac analysis, transient analysis and harmonic distortions are incorporated to verify the theory.     

Effect on Mechanical Performance of UHMWPE/HDPE-Blend Reinforced with Kenaf,Basalt and Hybrid Kenaf/Basalt Fiber

The aim of this study was to investigate the performance of UHMWPE/HDPE-reinforced kenaf, basalt and hybrid kenaf/basalt composites. Mechanical testing of these samples was carried out such as tensile, flexural (three-point bending) and an impact test (Charpy). Pure resin (UHMWPE/HDPE) samples were tested and compare with reinforced 10% weight fraction of kenaf, basalt and hybrid kenaf/basalt samples to identifying their contribution and potential in this new composite material. UHMWPE/ HDPE sample was produced in constant ratio 60:40 respectively via extrusion process. Basalt reinforced UHMWPE/HDPE generates the highest elastic modulus result compared to kenaf and hybrid kenaf/basalt as a reinforcement material. The tensile results of kenaf reinforcement UHMWPE/HDPE samples are significantly higher (20%) than pure blend resin, which is an indication for good performance of kenaf, basalt and hybrid kenaf/basalt to be used in UHMWPE/HDPE-blend polymers. The flexural and Charpy strengths show the drawback results, where performance of polymer is reduced 5% with the absence of kenaf. It can be concluded that kenaf, basalt and hybrid kenaf/basalt fiber successfully increase the UHMWPE/HDPE blends performance especially under tensile loading.     

Electrical and dielectric properties of lithium manganate nanomaterials doped with rare-earth elements

Substituted LiR_xMn_2 − xO₄ (R = La³⁺, Ce³⁺_, Pr³⁺ and x = 0.00 − 0.20) nanoparticles are prepared by the sol–gel method and the consequent changes in their lattice structure, dielectric and electrical parameters are determined by XRD, ED-XRF, SEM, LCR meter bridge and dc electrical resistivity measurements. Diffraction data show that the samples are single-phase spinel materials with crystallites sizes between 21 and 38 nm. The lattice parameter, cell volume and X-ray density are found to be affected by doping the Li-manganate with the rare-earth elements. The ED-XRF analysis confirms the stoichiometric composition of the synthesized samples and SEM reveals their morphology. Calculated values of the dielectric constant (?) and the dielectric loss (tan δ) decrease with the frequency of the applied field. This is attributed to Maxwell–Wagner polarization. Replacement of manganese by the rare-earth elements results in an improvement in the structural stability of the material, which is considered to be useful for enhancement of the cycleability of the compounds when used in lithium rechargeable batteries, and increases significantly the values of ? and tan δ (except for Ce). Lithium manganate nanomaterials with high ? and low tan δ may be attractive for application in memory storage devices.     

Neutronic analysis for core conversion (HEU–LEU) of Pakistan research reactor-2 (PARR-2)

Neutronic analyses for the core conversion of Pakistan research reactor-2 (PARR-2) from high enriched uranium (HEU) fuel to low enriched uranium (LEU) fuel has been performed. Neutronic model has been verified for 90.2% enriched HEU fuel (UAl₄–Al). For core conversion, UO₂ fuel was chosen as an appropriate fuel option because of higher uranium density. Clad has been changed from aluminum to zircalloy-4. Uranium enrichment of 12.6% has been optimized based on the design basis criterion of excess reactivity 4 mk in miniature neutron source reactor (MNSR). Lattice calculations for cross-section generation have been performed utilizing WIMS while core modeling was carried out employing three dimensions option of CITATION. Calculated neutronic parameters were compared for HEU and LEU fuels. Comparison shows that to get same thermal neutron flux at inner irradiation sites, reactor power has to be increased from 30 to 33 kW for LEU fuel. Reactivity coefficients calculations show that doppler and void coefficient values of LEU fuel are higher while moderator coefficient of HEU fuel is higher. It is concluded that from neutronic point of view LEU fuel UO₂ of 12.6% enrichment with zircalloy-4 clad is suitable to replace the existing HEU fuel provided that dimensions of fuel pin and total number of fuel pins are kept same as for HEU fuel.     

Synthesis and Characterization of Fe_(50)Cr_(14)Mo_(14)C_(14)B_6Gd_2 Bulk Amorphous Steel

Bulk amorphous steel having 7 mm thickness was synthesized to evaluate its thermal stability and mechanical properties.The steel was synthesized by Cu mold casting technique using 1-2N pure metals.Characterization of the material was done by X-ray diffraction,differential scanning calorimetry and scanning electron microscopy.The activation energies were calculated by Kissinger equation and it was found that the steel had better stability against crystallization.Mechanical properties like Vicker s hardness,n...     

Modelling and Analysis of Electro‐chemical,Thermal, and Reactant Flow Dynamics for a PEM Fuel Cell System

In this paper an approach for the dynamic modelling of polymer electrolyte membrane fuel cells is presented. A mathematical formulation based on empirical equations is discussed and several features, exhibiting dynamic phenomena, are investigated. A generalized steady state fuel cell model is extended for the development of a method for dynamic electrochemical analysis. Energy balance and reactant flow dynamics are also explained through physical and empirical relationships. A well‐researched system (Ballard MK5‐E stack based PGS‐105B system) is considered in order to understand the operation of a practical fuel cell unit. Matlab‐SIMULINK^TM has been used in simulating the models. The proposed method appears to be relatively simple and consequently requires less computation time. Simulation results are compared with available experimental findings and a good match has been observed.     

Enhancement of electrical resistivity of Sr0.5Ba0.5Fe12O19 nanomaterials by doping with lanthanum and nickel

From the viewpoint of electronic and telecommunication devices, the electrical resistivity is required to be high to curb the eddy current losses for efficient performance at high frequencies. In the present work, Sr_0.5Ba_0.5Fe₁₂O₁₉ hexaferrite has been doped with a binary mixture of lanthanum and nickel using chemical co-precipitation method of synthesis. The crystallite size of the synthesized samples is estimated in the range of 36–58 nm and their structural analyses have confirmed a single magnetoplumbite phase. The magnitude of the dc-electrical resistivity is enhanced, by almost 100 times, but Curie temperature (T_C) is reduced by doping with La–Ni, which has been explained on the basis of the exchange interactions. In addition, the doped samples exhibit very low dielectric constant (έ = 11–13) and low dielectric loss tangent (tan δ = 0.07–0.10) determined at a frequency of 1 MHz. These characteristics may be suitable for their potential application in electromagnetic attenuation materials and microwave devices.