Recently, discontinuous polymer flooding has been proposed and successfully applied in some offshore oilfields. The performance of discontinuous polymer flooding depends on various operational ...parameters, such as injection timing, polymer concentrations, and crosslinker concentrations of four types of chemical slugs. Because the number of the operational parameters are large and they are nonlinearly related, the traditional reservoir numerical simulation might not simultaneously obtain the optimal results of these operational parameters. In this study, to simulate the discontinuous polymer flooding processes, a simulation model was built using a commercial reservoir simulator (CMG STARS), in which the mechanisms of the four types of chemical slugs were considered, such as polymer viscosification, adsorption, and degradation. Then, a PSO–ICA algorithm was developed by using the PSO algorithm to improve the exploration ability of the ICA algorithm. The codes were written with MATLAB and linked to CMG STARS to perform optimization processes. Finally, the PSO–ICA algorithm was compared with the ICA and PSO algorithms on benchmark functions to verify its reliability and applied to optimize a discontinuous polymer flooding process in a typical offshore oilfield in Bohai Bay, China. The results showed that the developed PSO–ICA algorithm had lower iteration numbers, higher optimization accuracy, and faster convergence rate than these of PSO and ICA, indicating that it was an effective method for optimizing the operational parameters of discontinuous polymer flooding processes. Compared to the continuous polymer flooding, the discontinuous polymer flooding had a higher oil production rate, a lower water cut, and a lower residual oil saturation. The net present value of the optimal scheme of discontinuous polymer flooding reached 7.49 × 108 $, which is an increase of 6% over that of the scheme of continuous polymer flooding. More research including selecting more reasonable parameters of the PSO–ICA algorithm to increase its optimization accuracy and convergence rate, comparing with other available optimization algorithms, and verifying the performance of the optimal scheme of discontinuous polymer flooding in the practical offshore oilfield will be required in the future.
This paper presents a new design method for a capacitor-loaded cross-coupled cavity filter, which significantly increases the power capacity of the cavity filter while improving out-of-band ...rejection. The filter uses a coaxial resonator at the open end of the donut capacitive-load. A triangular form of cavity structure is used for the full-cavity arrangement to reduce the size of the filter. In order to validate the design, a filter with a center frequency of 2.08 GHz and bandwidth of 80 MHz was designed, processed, and tested. The measured insertion loss was ≤0.97 dB, and the return loss was >20 dB in the range of 2040 MHz to 2120 MHz; the rejection was as high as 80 dB, and in-band ripple was 0.06 dB in the upper and lower stopband-range, which was only 30 MHz away from the sideband. After a simulation of the model using HFSS software (HFSS 2021, Canonsburg, PA, USA), the measured results matched the simulation results, which verified the correctness and practicality of the design. Compared with the ordinary-disc-load resonant cavity, the new donut capacitively loaded cavity-bandpass-filter has a 13.2% reduction in height and a 29.7% increase in power capacity.
Ti-substituted NiZnCo ferrite thin films, Ni0.4Zn0.5TixCo0.1Fe2−xO4 (0≤x≤0.12), were synthesized by the sol–gel process. The structure and static magnetic properties of Ni0.4Zn0.5TixCo0.1Fe2−xO4 ...ferrite thin films have been investigated. There is a little increase of lattice parameter with Ti substitution. The average grain size of Ti-substituted NiZnCo ferrite thin films increased with Ti substitution. The saturation magnetization gradually increased with the increase of Ti substitution when x≤0.06, and decreased when x>0.06. Meanwhile, the coercivity initially increased with the increase of Ti substitution when x≤0.03, and decreased when x>0.03.
•There is a little influence on the lattice parameter with Ti substitution.•The average grain size of Ti-substituted NiZnCo ferrite thin films increases with Ti substitution.•The saturation magnetization gradually increased with the increase of Ti substitution when x≤0.06, and decreased when x>0.06.•The coercivity initially increased with the increase of Ti substitution when x≤0.03, and decreased when x>0.03.
► The diffraction peak shifted towards the lower angle and the lattice parameter increases with Zr substitution. ► The average grain size of Zr-substituted NiZn ferrite thin films increased with Zr ...substitution. ► Proper concentration of Zr substitution can improve the static magnetic properties of NiZn ferrite thin films.
Zr-substituted NiZn ferrite thin films, Ni0.5Zn0.5ZrxFe2−xO4 (0⩽x⩽0.2), were synthesized by sol–gel process. The structure and magnetic properties of Ni0.5Zn0.5ZrxFe2−xO4 ferrite thin films have been investigated. The diffraction peak shifted towards the lower angle and the lattice parameter increased with Zr substitution. The average grain size of Zr-substituted NiZn ferrtie thin films increased with Zr substitution. The saturation magnetization gradually increased with the increase of Zr substitution when x⩽0.10, and decreased when x>0.10. Meanwhile, the coercivity initially decreased with the increase of Zr substitution when x⩽0.10, and increased when x>0.10.
Co-substituted NiZn ferrite thin films, Ni0.5Zn0.5CoxFe2−xO4 (0≤x≤0.2), were synthesized by the sol–gel process. The structure and magnetic properties of Ni0.5Zn0.5CoxFe2−xO4 ferrite thin films have ...been investigated. The diffraction peak shifted towards the lower angle and the lattice parameter increased with Co substitution. There is little influence of Co substitution on the microstructure of NiZn ferrite thin films. The saturation magnetization gradually increases with the increase in Co substitution when x≤0.10, and decreases when x>0.10. Meanwhile, the coercivity initially decreases with the increase in Co substitution when x≤0.10, and increases when x>0.10.
► The diffraction peak shifts towards the lower angle and the lattice parameter increases with Co substitution. ► There is little influence of Co substitution on the microstructure of NiZn ferrite thin films. ► Proper concentration of Co substitution can improve the magnetic properties of NiZn ferrite thin films.
•We prepared NiZn ferrite doped FeSiAl-based thin films using oblique deposition technique.•The magnetic properties of FeSiAl-based thin films were systematically studied.•Two ferromagnetic resonance ...peaks were observed in the permeability spectra.•The thermal stability of microwave properties of FeSiAl-based films was studied.•The thermal stability of properties we studied was relatively good.
In this study, we comprehensively investigate the dynamic magnetic properties of FeSiAl-NiZnFeO thin films prepared by the oblique deposition method via a shorted microstrip perturbation technique. For the films with higher oblique angle and NiZn ferrite doping amount, there are two ferromagnetic resonance peaks observed in the permeability spectra, and both of the two peaks originate from FeSiAl. Furthermore, the magnetic anisotropy field HK of the ferromagnetic resonance peak at higher frequency is enhanced with increasing doping amount, which is interpreted in terms of the contribution of reinforced stress-induced anisotropy and shape anisotropy brought about by doping elements and oblique sputtering method. In addition, the thermal stability of the ferromagnetic resonance frequency fFMR of FeSiAl-NiZnFeO films with oblique angles of 35° and 45° with respect to temperature ranging from 300K to 420K is deteriorated with increasing ferrite doping amount, which is mainly ascribed to the influence of pair-ordering anisotropy and/or the reduction of the FeSiAl grain size.
The effects of sintering temperature and Bi2O3 content on the microstructure and magnetic properties of lithium-zinc (LiZn) ferrites prepared by a conventional ceramic method were investigated. The ...results show that the densification behavior and grain growth rate were greatly improved by the addition of Bi2O3, because a liquid phase sintering occurred during the sintering process at high temperature due to the low-melting point of Bi2O3 (825 deg C). X-ray diffraction (XRD) patterns of the slightly doped samples did not reveal the appearance of any phase other than spinel LiZn ferrite. However, the secondary phase of perovskite BiFeO3 was detected for Bi2O3 content of more than 0.25wt%. The studies further show that Bi oxide was present at grain boundary, and promoted the grain growth as reaction center at lower temperature. A high saturation magnetization, squareness ratio, minimum ferromagnetic resonance linewidth and low coercive force were obtained for the sample with 1.00wt% Bi2O additive at lower sintering temperature (1100 deg C).
FeSiAl soft magnetic composites (SMCs), which are widely used in electromagnetic applications, can be described as FeSiAl particles surrounded by electrical insulating layers. In general, good ...insulation is required to minimize eddy currents within SMCs in high frequency applications. In this work, FeSiAl-based SMCs with uniform single insulation layer of AlN/Al2O3 were prepared by high-temperature selective nitridation and oxidation. For comparison, SMCs with double layers of phosphate-resin or phosphate-silane were produced by traditional chemical process. Their magnetic properties were systematically studied. The results revealed that the core insulated by AlN/Al2O3 with high electrical resistivity had much better stability in the real part of permeability μ′ than double layer insulated cores with respect to frequency in the range of 100 kHz to 28 MHz. In addition, the FeSiAl-AlN/Al2O3 core had higher quality factor Q at higher frequency than other cores. The investigation of the effects of annealing process up to 600 °C on the cores indicated that the magnetic properties of FeSiAl-AlN/Al2O3 cores were strongly improved in terms of μ′, Q, total core loss Ptot and coercivity HC mainly on account of the hysteresis loss reduction by stress relaxation and defects elimination. By contrast, annealing treatment had less positive effects on the properties of the cores with double insulating layer. In addition, the microstructure, composition and thermal stability of the AlN/Al2O3 insulated particles were characterized by Scanning Electron Microscopy, Transmission Electron Microscopy, X-Ray Diffraction, X-ray Photoelectron Spectroscopy and Derivative Thermogravimetric Analysis, respectively.
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•FeSiAl-AlN/Al2O3 SMCs were prepared by simple selective nitridation and oxidation.•SMCs prepared by simple novel method and complicated traditional method were compared.•FeSiAl-AlN/Al2O3 core exhibited much better magnetic properties than traditional ones.•Annealing further improved the magnetic properties of FeSiAl-AlN/Al2O3 core evidently.
MnZn ferrites with the chemical formula Mn
0.700−
x
Zn
0.233Co
x
Fe
2.067O
4 have been prepared by conventional ceramic technique. Toroidal cores were sintered at 1350
°C for 4
h in N
2/O
2 ...atmosphere with 4% oxygen. Then the influence of Co-substitution on the temperature dependence of electromagnetic properties in MnZn ferrites were investigated by measuring the magnetic properties and DC resistivity over a wide temperature ranging from 25 to 120
°C. The results show that Co-substitution in MnZn ferrites results in the temperature of secondary maximum peak in the curve of initial permeability versus temperature and the lowest power loss shift to lower temperature. The Curie temperature, resonance frequency, DC resistivity and the activation energy of electron hopping increase with the increase of Co-substitution. Moreover, the drift mobility decreases with the increase of Co-substitution. However, there is little influence of Co-substitution on the microstructure with the increase of Co-substitution.
Crystallization kinetics of the sputtered SmCo based permanent magnetic films was investigated by differential scanning calorimeter, x-ray diffraction, and atomic force microscope methods. The ...results show that the apparent activation energy for crystallization is observed as 173.7kJ/mol, and the local activation energy for crystallization decreases with increasing crystal phase transformation fraction in non-isothermal crystallization. For isothermal crystallization, the apparent activation energy for crystallization is 159.8kJ/mol. The local activation energy for crystallization exhibits non-monotonic dependence on the crystal phase transformation fraction. The crystallization mechanism is obtained from the investigation of Avrami exponent and microstructure.
► Crystallization kinetics of the SmCo based magnetic films has been investigated. ► Important parameters for crystallization have been calculated. The crystallization mechanism has been found to be one-dimensional nucleation and growth.
