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The pursuit of high-efficiency and zero-emission refrigeration technologies has spurred interest in electrocaloric (EC) refrigeration utilizing ferroelectric (FE) materials, where accurate characterization of the EC effect is crucial for comprehending its underlying physical mechanisms and for developing high-performance EC materials. In this study, we investigate the influence of unsaturated vs saturated FE polarization characteristics on EC effects using Pb0.99Nb0.02[(Zr0.6Sn0.4)0.85Ti0.15]0.98O3 ceramics. Direct EC measurement reveals that unsaturated loops can introduce substantial errors and even fake negative EC effects when employing the Maxwell approach for indirect EC measurement. In contrast, relatively accurate indirect EC results can be obtained using saturated FE hysteresis loops. Furthermore, it also highlights the necessity for saturated polarization conditions to achieve optimal EC performance in FEs. This work not only emphasizes the importance of carefully selecting polarization data for indirect EC measurements, but also presents a universal strategy to enhance EC effects in various materials. [ABSTRACT FROM AUTHOR]

To maximize the recovery of coal seam gas and optimize the input-output ratio, the research of restoring production potential of shut-in wells of CBM is particularly important. According to the geological and producing characteristics of coal seam gas wells, five second-order indicators were confirmed, including geological conditions, supply capacity, sand production rate, production history and production status of surrounding wells, and their corresponding third-order indicators. To exclude the geology and regionalization influences of parameters, the evaluation index was defined to normalize the parameters, and using analytic hierarchy process (AHP) to confirm the weight, and then the evaluation model of restoring production potential of shut-in wells was built. The model was applied to the shut-in wells in Surat Basin, restoring production potential order of the wells was got according to the results, and the restoring measures were made, the results showed that the restoring production was good, at the same time the cost was reduced.

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. [ABSTRACT FROM AUTHOR]

It is necessary to use high-permittivity dielectric ceramics to realize various distributed microwave components in low-temperature co-fired ceramics (LTCC) structures. In this study, the Ba3.75Nd6.5Sm3Ti17.5(Cr0.5Nb0.5)0.5O54 (BNSTCN) ceramic was doped by Li2O–ZnO–B2O3 (LZB) glass to get the densification temperatures of lower than 960 °C. The effects of the LZB glass content on the wetting behavior, densification, and microwave properties were examined. The results showed that the BNSTCN + 4-wt% LZB sample sintered at 950 °C had outstanding microwave dielectric properties: dielectric constant (εr) of 67.5, quality factor (Q×f) of 5,186 GHz, and temperature coefficient of resonance frequency (τf) of − 0.6 ppm/°C. Besides, the BNSTCN + 5-wt% LZB sample sintered at 950 °C also presented good microwave dielectric properties: ɛr = 67.9, Q×f = 4,733 GHz, and τf = − 3.6 ppm/°C. [ABSTRACT FROM AUTHOR]

The perovskite-structured CaTiO3-based microwave dielectric ceramics play an essential role in the technical field of communication. This study is intended to obtain a temperature-stable Ca-Li-Nd-Ti microwave dielectric ceramic and explore the changing mechanism of dielectric properties. So the (Ca0.61Nd0.26)1-x(Li0.5Nd0.5)xTi0.96(Al0.5Nb0.5)0.04O3 (0 ≤ x ≤ 0.8, shorted as CLNTAN) microwave dielectric ceramics were designed, prepared and characterized in this paper. All constituents form a single phase of orthorhombic perovskite. SEM images verify that the polygonal grains gradually become cubic morphology as the x value increases for CLNTAN samples. Raman spectra show a distinct blue shift of vibrational modes by increasing the x value, and the broadened Raman peaks indicate a declined tendency of Q × f value. Interestingly, the εr values of samples reach the maximum at x = 0.7, then decrease as the x value increases. This finding is related to the bond valence at B-site. In addition, the τf values of samples exhibit a decreased tendency, and the temperature-stable (τf = –1.4 ppm/°C) CLNTAN ceramic with a high εr value of 129.2 was obtained at x = 0.76 when it was sintered at 1230 °C. [ABSTRACT FROM AUTHOR]

We investigated the relationship between magnetic properties of MnZn ferrites and [Fe.sub.2][O.sub.3] stoichiometry by measuring magnetic properties, electrical resistivity, and density. We used a scanning electron microscope to observe the fractured surface of sintered samples. MnZn ferrites were prepared by adapting the conventional ceramic technique. Toroidal cores were sintered at 1355[degrees]C for 4 h with 4% oxygen. The results show that the initial permeability and power losses of MnZn ferrites strongly depend on the content of [Fe.sub.2][O.sub.3]. And there is an obvious secondary maximum peak in the curve of [[mu].sub.i] versus T at about 100[degrees]C. The initial permeability [[mu].sub.i] reaches a maximum value and the power loss is lowest over a wide temperature ranging from 20[degrees]C to 180[degrees]C when the content of [Fe.sub.2][O.sub.3] is 52.5 mol%. Index Terms--[Fe.sub.2][O.sub.3], initial permeability, MnZn ferrites, power loss, temperature dependence.