Polarization Phenomena Research Articles

Helical strip-type spacers for enhanced multi-directional mixing and mitigation of temperature polarisation in membrane distillation – A numerical and experimental investigation

Membrane distillation (MD) is a promising membrane separation process, capable of achieving low energy consumption and yielding high-purity products. However, temperature and concentration polarisation phenomena take place adjacent to membranes, resulting in diminished MD performance. The insertion of spacers between membrane sheets is thought to be a potential solution, enhancing fluid mixing. In this study, we present a new helical strip-type spacer designed for efficient mixing and polarisation mitigation and compare its performance with conventional double-layer spacers via computational simulations. Simulation results reveal that the helical strip-type spacers outperform conventional double-layer spacers by up to 27 % in terms of average water flux, which is attributed to multi-directionally disturbed flow patterns facilitated by the strip swirl design. However, it is important to note that the pressure drop increases by a maximum of 1.9 times. Also it is experimentally demonstrated that the unique shape of the proposed spacer can be practical in MD through 3D printing, showing the same trends of the helix spacers having higher water fluxes than the conventional design by up to 20 %. In conclusion, the proposed spacers can efficiently promote near-wall fluid mixing and be beneficial in high recovery MD where severe polarisation can lead to membrane scaling, albeit at the cost of increased pressure loss.

Preliminary Exploration of Coverage for Moon-Based/HEO Spaceborne Bistatic SAR Earth Observation in Polar Regions

To address the challenge of achieving both temporal consistency and spatial continuity in Earth observation data of polar regions, this paper proposes an innovative concept of Moon-based/Highly Elliptical Orbit (HEO) Spaceborne Bistatic Synthetic Aperture Radar (MH-BiSAR), with transmitters on the Moon and receivers on HEO satellites. By utilizing ephemeris data and an orbit propagator, this study explores MH-BiSAR’s geometric coverage capabilities in polar regions and conducts a preliminary analysis of its characteristics. The findings reveal that MH-BiSAR could provide continuous multi-day revisit observations of polar regions within each sidereal month, presenting a significant advantage for monitoring high-dynamic and large-scale scientific phenomena, such as polar sea ice observations. This innovative observational method offers a new perspective for polar monitoring and is expected to deepen our understanding of polar phenomena.

Synergistic effects of Li-based ferrite and graphene oxide in microwave absorption applications

The successful fabrication of composites consisting of ferrites with a composition of Li0.4Mg0.25Zn0.25Fe2.2O4 and Graphene oxide was carried out using the ultra-sonication technique. The current study examined the impact of graphene oxide in spinel ferrite employing X-ray diffraction, dielectric, and magnetic susceptibility studies. The X-ray diffraction investigation confirmed the spinel phase formation in ferrite and graphene oxide synthesis. The measured range for the size of crystallites was found to be between 48.43 and 30.07 nm. The DC resistivity of cubic ferrite at room temperature was determined to be 1.715 ×1010 ohm-cm by a two-probe approach. Furthermore, it was observed that the resistivity fell significantly as the content of graphene oxide increased. The dielectric constant exhibited behavior consistency with the Maxwell-Wagner phenomenon of interfacial polarization. The rise in graphene oxide content in ferrite results in high AC conductivity of composites due to the relatively large value of conductivity of graphene oxide and the improved charge hopping mechanism. The magnetic susceptibility of all the samples demonstrated a progressive decline as the temperature increased, which can be attributed to the disruption of spin alignment at the Curie temperature. The observed Curie temperature of all samples was 413–473 K. Integrating spinel ferrite with Graphene oxide has significantly improved the magneto-electrical characteristics, indicating potential applications in supercapacitors, high-frequency electromagnetic devices, and microwave absorption.

Evolution and driving factors of inequality in CO2 emissions from agricultural energy consumption in China

The inequality in CO2 emissions from agricultural energy consumption is a major challenge for coordinating low-carbon agricultural development across regions in China. However, the evolutionary characteristics and driving factors of inequality in China’s agricultural energy-related CO2 emissions are poorly understood. In response, the Kaya–Theil model was adopted to examine the three potential factors influencing CO2 emission inequality in China’s agricultural energy consumption. The results revealed that, from 1997 to 2021, agricultural energy-related CO2 emissions per capita showed a significant upward trend, with prominent polarization and right-tailing phenomena. Overall, the inequality was on a downward trend, with the Theil index falling from 0.4109 in 1997 to 0.1957 in 2021. Meanwhile, the decomposition of the national inequality revealed that the within-group inequality declined from 0.3991 to 0.1634, which was greater than between-group inequality, based on zoning the 28 provinces into three grain production functional areas. As for the three kaya factors, the energy intensity contributed the most to the overall inequality, followed by the agricultural economic development and CO2 emission intensity. Based on these results, this study provided some potential strategies to reduce agricultural-related CO2 emissions.

Research on the Asymmetric Phenomenon of Voltage Polarity Based on Dielectric Wetting.

The present research investigated the voltage polarity asymmetry phenomenon based on dielectric wetting. In an ITO-hydrophobic layer-droplet setup, three reagents with different pH values (3.96, 7.0, and 10.18), two types of hydrophobic materials (AF1601 and 6%T6), and two different thicknesses (340 nm and 2.5 μm) of each material were systematically investigated. The results show that the thickness of the hydrophobic dielectric layer and the pH of the droplets had a significant impact on the droplet contact angle variation with the voltage. The contact angle on the thick hydrophobic dielectric layer followed the Lippmann-Young equation as the voltage changed. The angle of the thin hydrophobic dielectric layer was affected by its own properties and the type of droplet, which led to the occurrence of voltage polarity asymmetry of the electrowetting phenomenon. After further investigation of this phenomenon, it was found that it mainly accounted for the decrease in electric field strength at both ends of the droplet, which was caused by electrochemical reactions and changes in circuit resistance. The leakage current is an important indicator, and this phenomenon can be prevented by increasing the thickness of the hydrophobic dielectric layer.

Introduction: The New Polarization in Latin America

ABSTRACT Mounting evidence suggests that Latin American democracies are characterized by politics and societies becoming more divisive, confrontational, and polarized. This process, which we define here as the “new polarization” in Latin America, seems to weaken the ability of democratic institutions to manage and resolve social and political conflicts. Although recent scholarship suggests that polarization is integral to contemporary patterns of democratic “backsliding” seen in much of the world, this new polarization in the region has not yet received systematic scholarly attention. Aiming to address this gap in the literature, the different contributions in this special issue revise the conceptualization, measurement, and theory of a multidimensional phenomenon such as polarization, including both its ideological and affective dimensions, as well as perspectives at the elite and mass levels of analysis. Findings shed light on the phenomenon of polarization as both a dependent and an independent variable, contributing to comparative literature on polarization and its relationship to democratic governance.

Bulk resistance and contact impedance: Particular solution for annulus, homogeneous domain and dimensional analysis of the complete electrode model

Viewing the complexity of multiphase flows, in which multi-dimensional and time-changing fluid structures, known as flow patterns, must be captured, electrical impedance tomography (EIT) stands out as an alternative for fluid flow visualization. Using an EIT system, this study presents an enhanced approach for measuring film thickness in two-phase flows. Incorporating bulk resistance and contact impedance contributions, the proposed ohmic model significantly improves accuracy, particularly in low-conductivity scenarios, yielding a robust, accurate, and rapid technique for obtaining images from an EIT-based low-cost acquisition system. Tomographic experiments validate the model’s efficacy using cylindrical sensors and diverse conductivity mediums, including two distinct phantoms. The dimensional analysis of the model yields five dimensionless numbers, revealing interrelations between electrical parameters and sensor construction. A correlation based on a dimensionless number for the contact impedance is obtained. Additionally, the experiments demonstrate a strong interplay with the polarization phenomenon.

Deep exclusive meson production as a probe to the puzzle of Λ hyperon polarization

In the 1970s, an unexpected transverse Λ polarization in unpolarized proton-beryllium collisions was discovered, which initiated extensive studies on spin phenomena in high-energy physics. Over the past five decades, similar transverse Λ polarization has been observed across various collision systems, including lepton-hadron deep-inelastic scattering, hadron-hadron collisions, and electron-positron collisions. Despite numerous promising theoretical models, the fundamental mechanism underlying this polarization phenomenon remains inconclusive to this day. However, in both longitudinally and transversely polarized lepton-hadron and hadron-hadron collisions, it is found that the Λ hyperon is polarized with respect to the initial parton spin direction. How the Λ hyperon acquires its spin has become one of the most crucial questions to address in order to resolve this puzzle. In this paper, I propose to use an exclusive process that can be measured at the Electron-Ion Collider, the deep exclusive meson production, to explicitly test the mechanism of Λ polarization. The outcomes of this experimental measurement are anticipated to unveil the dominant mechanism by which Λ obtains its spin, eliminating many of the ambiguities that have been encountered in previous studies. Finally, experimental challenges and requirements are discussed. Published by the American Physical Society 2024

High frequency enhancement of dielectric constant, crystal structure analysis, and magnetic properties of Pr3+- Zn2+ substituted Co2Y-type barium hexagonal ferrites

The effect of Pr3+-Zn2+ doping on the magnetic and dielectric properties of Co2Y-type barium hexaferrites with the chemical composition Ba2Co2Fe12-x-yPrxZnyO22 (x = 0.00, 0.10, 0.20, and y = 0.00, 0.15, 0.25), was investigated in this study. The prepared Pr3+-Zn2+ substituted Co2Y-type barium hexaferrites were calcined for 5 h at 1100 °C in a digital heating chamber. The XRD analysis confirms the presence of a crystalline phase in the undoped Co2Y-type barium hexaferrite samples, with a space group identified as R-3m. Characteristic absorption bands of Co2Y-type barium hexaferrites were observed at 540 and 422 cm−1 due to the asymmetric stretching vibration of Fe3+ and O2− at both, octahedral and as well as tetrahedral crystallographic sites. The magnetic interaction between the particles causes slight agglomeration. Dielectric and impedance spectroscopy were performed using Koop's phenomenological theory and the Maxwell-Wagner two-layer dielectric relaxation model. The ε′ was found to decrease with an increase in applied frequency due to the space-charge polarization phenomenon. The rise in ε′ at higher frequencies enhances the material's suitability for high-frequency applications. The magnetic parameters were extracted from the M − H hysteresis loop, and it was observed that they were affected by the site preferences of Pr3+ and Zn2+. The prepared Y-type hexaferrite's optimized magnetic parameters make it a good option for magnetic memory applications.

High performance Zn–Al LDH modified forward osmosis membrane with antibacterial, anti-membrane fouling, and photocatalytic degradation ability

Forward osmosis membrane has shown great potential in the fields of seawater desalination and sewage treatment. However, the concentration polarization phenomenon and membrane fouling in the water treatment process greatly reduce the water treatment performance and restrict its application. To address these challenges, we employed a pre-buried seed-in-situ growth method to facilitate the Zn–Al layered double hydroxide (Zn–Al LDH) growth on the thin nanofiber membrane, and use it as the support layer for the preparation of a Zn–Al LDH modified forward osmosis membrane. Studies have shown that the introduction of Zn–Al LDH significantly improves the water treatment efficiency of the forward osmosis membrane (In Al-DS mode, the water flux increased by 87.5 %, up to 50.50 LMH, with a low specific salt flux of 0.13 g L−1). It also exhibits exceptional antibacterial, anti-membrane fouling, and photocatalytic degradation properties. This research presents a novel approach for the development of advanced high-efficiency forward osmosis membranes.

Study on the Efficiency, Evolutionary Trend, and Influencing Factors of Rural–Urban Integration Development in Sichuan and Chongqing Regions under the Background of Dual Carbon

Re-evaluating how urban and rural development can be integrated is a necessary step towards achieving the “dual-carbon” objective and facilitating a thorough transition towards a green and low-carbon economy and society. This study empirically investigates the geographical disparities, evolving patterns, and determinants of the effectiveness of urban–rural integration development in Sichuan and Chongqing. Results of the study indicate that (1) the effectiveness of urban–rural integration development in Sichuan and Chongqing is generally poor, and external environmental factors adversely affect the urban–rural integration of economically developed cities; (2) the urban–rural integration development efficiency in Sichuan and Chongqing does not show a more obvious polarization phenomenon, but the gap between the cities gradually widens; and (3) regarding influencing factors, market dynamics are favorable to overall urban–rural integration development in the Sichuan and Chongqing regions, while the development of the digital economy and the level of financial development can exacerbate the imbalance of regional urban–rural integration development. Based on this premise, pertinent policy suggestions are offered to facilitate the merger of urban and rural areas and foster efficient development in the regions of Sichuan and Chongqing.

Fast ionic conductor MnSe supported Micron-Si embedded in three-dimensional N-doped carbon matrix for lithium-ion batteries

Silicon is regarded as the most potential anode for the next generation lithium-ion batteries (LIBs) since its superhigh specific capacity and abundant reserves. Nonetheless, the grievous volume variation and inferior connate conductivity imped its further step on the commercial application. Herein, three-dimensional (3D) porous N-doped carbon microspheres, in which silicon is embedded and supported by MnSe, are fabricated via a simple spray drying method, named as MnSe/Si@NC. Such synergy conduces to the weaker polarization phenomenon and lower reactive barrier. Multi kind of electrochemical tests announce that the 3D network supported by MnSe and synthetical chemical bridge bonds, can remarkably ameliorate electron conductivity and structural stability. Benefit from the reasonably designed materials, the MnSe/Si@NC-10 anode expresses an outstanding cycling stability of 1030.8 mAh·g−1 at 2 A g−1 over 1000 cycles and extremely low-capacity loss rate for each cycle with about 0.27 ‰. In a word, this work can provide reference for the designing and preparation of high-performance anode materials utilized in LIBs.

The effect of clay modification on the structure, dielectric behaviour and mechanical properties of PVDF/PMMA/CTAMag polymer nanocomposites as potential flexible performance materials

Abstract In this approach, nanocomposites of PVDF/PMMA/CTAMag films have been successfully synthesized. Modified Maghnite was used as inorganic reinforcement. In this study, nanocomposite polymers were developed based on a mixed matrix of poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) of composition (80/20 w/w) in dispersion containing 0, 1, 3, 5 and 7 wt % fillers of organomodified montmorillonite nanoclay (CTAMag) in the melt state. The results obtained by scanning electron microscopy (SEM), XRD traces and FTIR spectra highlighted the homogeneous flexible character of the PVDF/PMMA/CTAMag films and their intercalated and intercalated/exfoliated surface morphology, in addition to the presence of PVDF α, β and γ phase crystallites in these complex films. The increased presence of the modified clay in the host matrix of the PVDF/PMMA blend significantly influenced the melting temperature and the degree of crystallinity of the PVDF crystallites. The scattering of the dielectric spectra, which covers a wide range of frequencies from 20 Hz to 1 GHz, indicates the presence of the phenomenon of interfacial polarization associated with the dielectric capacitance complex at lower frequencies in these composites at 27 °C. The mechanical properties of these composites were evaluated as a function of the load and the mixed matrix of these composites.

Sc3+ substituted Na3V2(PO4)3 on N-doped porous carbon skeleton boosting high structural stability and superior electrochemical performance for full sodium ion batteries

The poor structural stability and conductivity of Na3V2(PO4)3 (NVP) have been serious limitations to its development. In this paper, Sc3+ is selected to replace partial site of V3+ which can enhance its ability to bond with oxygen, forming the ScO6 octahedral unit, resulting in improved structural stability and better kinetic properties for the NVP system. Moreover, due to the larger ionic radius of Sc3+ compared to V3+, moderate Sc3+ substitution can support the crystal framework as pillar ions and expand the migration channels for de-intercalation of Na+, thus efficiently promoting ionic conductivity. The introduction of polyacrylonitrile (PAN) to provide an N-doped porous carbon substrate is another key aspect. The low-cost carbon resource of PAN can induce a beneficial nitrogen-doped carbon skeleton with defects, enhancing electronic conductivity at the interface to reduce the polarization phenomenon. The established pore structure can serve as a buffer for unit cell deformation caused by Na+ migration. Furthermore, the enlarged specific surface area provides more active sites for electrolyte infiltration, improving the material utilization rate. The after cycling X-ray Diffraction/scanning electron microscope (XRD/SEM) further confirms the stabilized porous carbon skeleton and improved crystal stability of Sc-3 material. Ex-situ XRD analysis shows that the crystal volume change in the Sc-3 cathode is relatively slight but reversible during the charge/discharge process, indicating that Sc3+ doping plays a crucial role in stabilizing the unit cell structure. The hybrid Sc/VO6 and PO4 units jointly build a strong bone structure to resist stress and weaken deformation. Accordingly, the optimized Sc-3 sample reveals an initial capacity of 115.9 mAh/g at 0.1C, with a capacity retention of 78.6 % after 2000 cycles at 30C. The Sc-3//CHC full battery can release a capacity of 191.3 mAh/g at 0.05C, accompanied by successful illumination, showcasing its promising practical applications.

Residential differentiation characteristics based on “socio-spatial” coupling: A case study of Zhengzhou

Residential differentiation transcends its physical aspect, necessitating attention to deeper issues such as group-based disparities underlying spatial configurations. This paper based on multiple data sources, utilizes indicator dimensionality reduction, spatial clustering, and indices of dissimilarity to conducts clustering and matching analysis of social groups and residential spaces. It summarizes and distills the social-spatial coupling types of residential differentiation in Zhengzhou city under a layered model, focusing on social spatial polarization and solidification phenomena in China, and proposing optimization and control recommendations. Findings include: (1) Residential space differences primarily manifest in pricing, while social group distinctions focus on consumption capacity and age. Residential differentiation is a process of continuous differentiation and interaction between two dimensions; (2) Urban housing types do not strictly align with socio-economic attributes, with six typical coupling types observed within the “inner city - new city - outskirts” framework; (3) The “filtering” effect of high housing prices in Zhengzhou leads to wealthy clustering in new city outskirts, while low-income groups aggregate in peripheral and declining inner-city areas, resulting in pronounced spatial segregation; (4) Urban residential differentiation reflects the interaction between macro-controls in the housing market and individual residential choices, serving as a spatial representation of social stratification outcomes.

Analysis of regional differences and evolution features for waterway transport efficiency in the Yangtze River Economic Belt considering undesired outputs

Waterway transport plays an increasingly important role in pursuing the sustainable development of the transportation industry and promoting regional economic development. Understanding the regional differences and evolution features of waterway transport efficiency (WTE) is a requisite for formulating waterway transport development policies. However, many studies of transport efficiency mainly focus on road, railway, and air transportation. Few studies have conducted an in-depth analysis of the WTE in the Yangtze River Economic Belt (YREB) from the perspective of considering undesired output. Adopting the Super slack-based measure (Super-SBM) model, Dagum Gini coefficient, and kernel density estimation as an analysis tool, this study explored the WTE’s region disparities and dynamic evolution features based on the data from 2011 to 2020 in YREB. The analysis results represent that: (1) there represented a fluctuating and slowly upward trend of waterway transport efficiency during the study period. (2) The midstream region has the highest waterway transport efficiency, followed by the upstream region, and last is the downstream region. (3) The regional disparities in waterway transport efficiency exist in YREB, and the primary source of these differences is the inter-regional difference. And (4) the polarization phenomenon and agglomeration characteristics of waterway transport efficiency in YREB are gradually weakened and decreased, respectively. In the end, this article summarized the implications of this study to improve the waterway transport efficiency and service capabilities in YREB.

Optimizing the economic viability of proton exchange membrane fuel cells operated with oxygen-enriched cathode air for residential hydrogen energy storage systems

The recovery and utilization of oxygen in residential hydrogen energy storage systems significantly impact economic factors. This study introduces an algorithm tailored to optimize oxygen concentration (fraction) across varied operational conditions, encompassing considerations for both efficiency (positive aspect) and lifetime (negative aspect). Initially, an enhanced air supply system (ASS), functioning with oxygen-enriched cathode air, is devised following the forefront scheme. Moreover, a dynamic model is formulated based on MATLAB/Simulink® software for the proton exchange membrane fuel cell (PEMFC) system. The model enables quantitative assessment of system gains in relation to various current densities and oxygen fractions, and its accuracy is partially validated through experimental data. Further, a model correlating stack lifetime to oxygen concentration (fraction) is established using experimental data obtained from other researchers. Finally, the optimal oxygen fractions are determined and managed, with a comparison of the effects before and after optimization. The optimized results indicate a 13% improvement in stack net power at rated operating conditions and a 24% improvement at peak operating conditions, and the system efficiency is improved by 24% and 43% at rated and peak operating conditions, respectively. In addition, the minimum value of system efficiency is observed to be 54%, and there is a notable attenuation of the concentration polarization phenomenon. This approach contributes to mitigating the challenge of lower system efficiency in normal PEMFCs for residential hydrogen energy storage systems (RHESSs) attributed to inadequate gas supply pressure.

Featuring vertical channel structure through directional solidification method to endow GNP-aerogels with enhanced ultra-electromagnetic wave absorption

Three-dimensional (3D) carbon-based electromagnetic waves absorbing materials (EWAMs) have garnered significant attention due to high electrical conductivity, high dielectric loss, low density, and improved characterization of impedance matching. However, there is a paucity of research on the design of material structures. In this regard, we proposed the graphene nanoplates (GNPs) EWAMs featuring a vertically aligned channel structure through liquid nitrogen rapid directional solidification and freeze-drying techniques. By utilizing methyl cellulose (MC) as a binder to modify the internal ice crystal structure, an exceptional electromagnetic waves (EWs) absorption material exhibiting excellent impedance matching characteristics and demonstrating multiple polarization phenomena were created. Notably, the material showcased superior absorption performance with a minimal reflection loss (RLmin) of −57.20 dB. Furthermore, the pre-solidification slurry possesses remarkable plasticity, facilitating the fabrication of various complex structures for EWAMs during directional solidification. This method provides novel insights for future exploration and fabrication of tuneable frequency band EWAMs.

Introducing Ce into the interface of NiCo LDH@PBAs to build multi core–shell electrode with superior stability of supercapacitor

Core-shell electrodes have been used in many fields, however, the poor conductivity caused by the weak interfacial interaction limits the practical application of the composites. Herein, a novel multi core–shell material (NiCo-Ce@PBAs) used as electrode in supercapacitor is prepared using Ce as bridge to connect the core (NiCo LDH) and shell (NiCo PBAs). Benefiting from the gradient orbital coupling of 2p-4f-π derived from O-Ce-C≡N unit sites in NiCo-Ce@PBAs, the composite shows enhanced covalency and determines to delocalize the electronic expansion in the interaction. Besides, the redox pair of Ce3+-Ce4+ also makes great contribution to expedite the charge transfer as well as enhancing the binding energies of metals in core and shell. Overall, the optimized core–shell electrodes show excellent electrochemical performance with high area-specific capacitance of 1847 F g−1 at 1 A g−1, which is much higher than that of LDH-based electrodes ever reported. In addition, the electrode is found better cyclic performance than the others (95.7 % even after 10,000 cycles), which is due to the fact that the special 4f empty orbits can store partial electrons, thus decreasing the polarization phenomenon. It also shows great practical application when using commercial activated carbon as cathode. This work illustrates a new strategy to construct core–shell electrodes with strong interfacial interaction as well as revealing the important role of orbital theory in the design of multi core–shell electrodes.

Theoretically designed epsilon-negative materials: Ni nanoparticles encapsulated CNTs and their magnetic driven properties

Epsilon-negative materials (ENMs), especially the materials with a weakly negative permittivity, hold significant value in various applications including electromagnetic absorption, solar energy harvesting, and sensing technologies. In this study, nickel (Ni) nanoparticles were synthesized and encapsulated within carbon nanotubes (Ni@CNTs). Subsequently, films composed of polyvinyl alcohol (PVA) and Ni@CNTs were fabricated (PVA/Ni@CNTs), demonstrating favorable magnetic driven performance and a broadband weakly negative permittivity. The negative permittivity was about -1500 from 10 kHz to 1 MHz. The presence of π electrons in carbon materials enhanced carrier mobility, providing the obtained negative permittivity with the advantage of low dispersion. Additionally, a noticeable polarization phenomenon took place at the interface of the two phases (PVA and Ni@CNTs), significantly increasing the positive permittivity to neutralize the negative permittivity. Moreover, this work firstly introduces magnetic-driven soft ENMs, broadening practical applications of such materials to magnetic-driven soft actuators and robotics. Theoretical calculations offer explanations of the mechanism, providing a foundation for designing the next generation of ENMs.