Coercivity Mechanism Research Articles

Working Without a Boss in Dhaka? Affective Labor, Ratings, And Temporalities in Digital Platforms

Abul Bashar—a ride-hailing driver from Dhaka—commented, “Uber allowed me to be my boss. Even if I drive throughout the day, no one has the right to rush or demand anything of me.” Despite such perception of flexibility, analyzing narratives of platform workers gathered in August 2020 and February 2021, in this article, it is argued that platform workers endure more stress providing their services than non-platform workers, such as driving for a private employer, because customer preferences change with every new trip. Additionally, they must work longer hours to be eligible for bonuses, and in any disputes, the platforms consider “passengers/customers are always right.” The article also reveals how digital platforms (ride-hailing or delivery) establish a coercive mechanism through their passengers’/customers’ rating system. Thereby, the article debunks the myth of democratization of work and revolutionizing the transportation/service system, identifying the affective regimes of work—that produce no material and durable goods but immaterial goods, such as comfort and ease for the customers—in digital platforms at Dhaka. Moreover, emphasis on affective labor and incentives results in disjunctive temporalities linked with family life and social routines, engendering modes of embodiment that constitute digital platform workers. Finally, the article argues that the affective regime generates forms of alienation and sociality that are co-implicated rather than opposing each other. Social Science Review, Vol. 41(1), June 2024, Page 195-214.

The ‘Digital Transformation for Development’ Anti‐Politics Machine: A Case Study on Global Digital Development Governance and Public‐Sector Digital Transformation in Uganda

ABSTRACTHegemonic digital transformation for development (DX4D) initiatives, global digital development initiatives concerning the public sector, function as a contemporary ‘anti‐politics machine’. This is evidenced by the global extractive and surveillant dynamics surrounding these initiatives' core projects, such as digital public infrastructures. Despite being a global policy initiative focusing on bureaucratic reform and infrastructural development, hegemonic DX4D initiatives are usually presented as technocratic and depoliticised transformations, obscuring the value‐extractive dynamics, network paradigms, infrastructural control mechanisms emerging around them, especially concerning digital sovereignty. The DX4D anti‐politics machine refers to depoliticised and value‐extractive global digital development policy initiatives extending the bureaucratic reach of state and non‐state actors into public systems while obscuring global hegemonic actors' advancement of infrastructural ideologies and use of coercive mechanisms to supplant the strategic interests of powerful global actors over the public value. The ‘DX4D anti‐politics machine' concept examines how infrastructural ideologies are operationalised through global development and humanitarian initiatives with implications for governments, governance, and well‐being. The ‘DX4D anti‐politics machine’ is empirically examined through a qualitative case study of several large‐scale foundational DX4D projects in Uganda. The DX4D anti‐politics machine's coercive dynamics and implications for many Global South countries are examined, and its conceptual contribution is discussed.

Transformation fate of bisphenol A in aerobic denitrifying cultures and its coercive mechanism on the nitrogen transformation pathway.

Bisphenol A (BPA) is a commonly used endocrine-disrupting chemical found in high levels in wastewater worldwide. Aerobic denitrification is a promising alternative to conventional nitrogen removal processes. However, the effects of BPA on this novel nitrogen removal process have rarely been reported. Herein, we investigated the removal and interaction effects of BPA (0, 0.1, 1, and 10 mg/L) in aerobic denitrifying cultures. Our experimental results demonstrated that the aerobic denitrification system could remove 66%-86% of BPA from wastewater. Fourier transform infrared spectroscopy revealed that polysaccharides and amides were the primary sites for adsorption. An increase in the type and number of intermolecular hydrogen bonds might enhance the ability of aerobic denitrifying cultures to adsorb BPA. Adsorption kinetics analysis demonstrated that inhomogeneous multilayer adsorption was the leading cause of BPA removal. Adsorbed BPA decreased the sedimentation, flocculation, and hydrophobicity of aerobic denitrifying cultures, triggering changes in the levels of proteins and polysaccharides in extracellular polymeric substances. As the influent BPA increased from 0 to 10 mg/L, the nitrate-nitrogen and total organic carbon in the reactor effluent increased from 0.4 ± 0.2 and 26 ± 7.9 mg/L to 18.8 ± 9.3 and 116.2 ± 55.6 mg/L, respectively. BPA (initial concentration range: 1-10 mg/L) significantly influenced the abundance of genes involved in the nitrogen transformation pathway, contributing to the increase in the abundance of gaseous NOx-transformed genes and altering the relative abundance of denitrifying bacteria, particularly Thauera. Correlation analyses revealed that Pseudomonas, Thauera, and AKYH767 are important for maintaining systemic nitrogen transformations and BPA adsorption.

Effects of grain boundary phases on recoil loops by in situ observation of magnetization behavior in nanocrystalline PrNd–Fe–B magnets

The grain boundary phase (GBP) has a significant influence on the magnetization behavior in nanocrystalline PrNd–Fe–B magnets. The current study demonstrates that reversible/irreversible magnetization behavior and the phenomenon of open recoil loops are related to both the nature of GBPs and the magnetization state by in situ observation. The optimization of GBPs nature (increase the volume fraction and improve the composition of GBPs) leads to the suppression of reversible magnetization behavior and the phenomenon of open recoil loops at low fields. Since the asymmetric magnetic domain structure appears only at low cycle fields, the openness phenomenon originates from the weak pinning grain boundaries (GBs). In addition, optimization of the GBPs also enhances pinning strength and uniformity, which contributes to the domain walls being pinned in the GBs at higher external fields. At this moment, the domain wall is dominated by irreversible magnetization behavior, and the openness phenomenon disappears. This proves that the coercivity mechanism is transformed from inhomogeneously weak pinning to homogeneously strong pinning with the optimization of GBPs. Consequently, the coercivity and squareness factor are significantly enhanced. This study sheds light on the understanding of the effects of GBP's nature on recoil loops and coercivity mechanism, and it also provides significant guidance for the development of advanced permanent magnets.

Synergy of soft and hard regulations in climate governance: The impact of state policies on local climate mitigation actions

AbstractSoft regulations refer to a wide range of quasi‐legal instruments enforced through non‐binding and less coercive mechanisms. They are becoming increasingly vital in environmental governance for addressing complex issues across multilevel government authorities. However, the impact of sub‐national state soft regulations on local governments has not received adequate scholarly attention. In this study, we compile a novel dataset of U.S. local government climate mitigation actions and state‐level climate policies from various sources. We test how state climate action plans—primary examples of soft regulation—along with four other state‐level hard regulations, influence local governments' climate mitigation actions. Our findings reveal that, while state climate action plans do not directly drive local governments' specific climate mitigation actions, they play significant roles in motivating local goal setting. In contrast, hard regulations, such as state policies that directly target CO₂ emissions, not only stimulate local goal setting on climate change but also promote direct climate mitigation actions. Moreover, our results demonstrate the interactive effect of soft and hard regulations in fostering intergovernmental collaboration on climate change.

Comparative view of coercivity mechanisms in soft and hard magnetic materials

The main differences between soft and hard magnetic materials are commented on. It is discussed how the coercivity mechanisms can be affected by the domain wall energy. A spherical cap nucleus is used for this analysis. There is a competition between magnetostatic energy and domain wall energy terms. As a consequence, for soft magnetic materials, the magnetostatic energy term is dominant over the domain wall energy term. An explanation for the dependence of the coercivity with grain size is presented. For grain size above the single domain size, in hard magnetic materials with high magnetocrystalline anisotropy, the coercivity decreases following a law proportional to the inverse of the square root of the grain size, whereas in soft magnetic materials, the coercivity reduces proportionally to the inverse of grain size.

Exploiting the positive effect of REFe2 (RE=rare earth) phase on coercivity in Nd-Ce-Fe-B sintered magnets

The REFe2 phase is inherent in high Ce content Nd-Ce-Fe-B magnets, and how to harness its existence and exert its beneficial effects on magnetic properties is an essential topic in the development of these magnets. In this work, we reveal the positive impact of the REFe2 phase on coercivity enhancement by designing the RE-rich B-lean composition in the Nd-Ce-Fe-B sintered magnet with 30 wt. % Ce replacing Nd. The coercivity in the as-sintered state attains 14.07 kOe and slightly increases to 14.54 kOe upon post-sinter annealing. Phase composition and microstructure analysis indicate that the Fe-storage effect of the REFe2 phase immobilizes a large amount of Fe elements in the triple junctions, resulting in the development of a continuous Fe-lean non-ferromagnetic grain boundary phase with thickness exceeding the exchange length. In addition, the magnetization and demagnetization behaviors were analyzed by the recoil loops to reveal the coercivity mechanisms. This work demonstrates that, in addition to improving wettability, the Fe-storage effect of the REFe2 phase positively influences coercivity.

Phase composition tailoring and coercivity mechanism of high-performance high-abundance rare-earth sintered magnets

Phase composition tailoring and coercivity mechanism of high-performance high-abundance rare-earth sintered magnets

Cu-doped nanocomposite Pr2Fe14B/α-Fe ribbons with high (BH)max

Abstract The melt-spun ribbons of nominal composition Pr9Fe84.2–x B6.2P0.3Zr0.3Cu x (x = 0, 0.5, 1, 2) were prepared at wheel speeds of 21 m·s−1, 27 m·s−1, 30 m·s−1, and 33 m·s−1. The XRD patterns show that as the wheel speed increases, the crystallinity of the 2:14:1 hard phase decreases, while that of the α-Fe soft phase increases. The (BH)max, remanence, and coercivity are improved from 63 kJ·m−3, 0.85 T, and 515 kA·m−1 for the Cu-free ribbons to 171 kJ·m−3, 1.08 T, and 684 kA·m−1 with x = 0.5. The high squareness ratio of J r/J s ∼ 0.82 at 0.5 at.% Cu (27 m·s−1) indicates strong exchange coupling due to small grain sizes of 15 nm and 30 nm for soft and hard magnetic phases, respectively. The SEM images revealed smooth morphology and uniform element distribution at 0.5 at.% Cu (27 m·s−1), contributing to the high magnetic properties. The low recoil permeability (μ rec) value of 5.466 × 10−4 T/kA·m−1 to 1.970 × 10−4 T/kA·m−1 confirms the strong exchange coupling with x = 0.5 (27 m·s−1). The initial magnetization curves show that the coercivity mechanism of the Cu-free alloy evolves from the nucleation of the reverse domain to the domain wall pinning as the wheel speed increases, resulting in a high coercivity value of 818 kA·m−1 (33 m·s−1). Conversely, for the Cu-added alloy, the coercivity mechanism changes from pinning to the nucleation of the reverse domain from low to high wheel speed.

Challenges in implementing COP 21 obligations in Brazil until 2022

The article examines the challenges Brazil faced in implementing its obligations under the Paris Agreement (COP 21) up to 2022, focusing on the agricultural, energy, and transportation sectors, while also addressing the political obstacles that complicated the process. The study highlights the need for an integrated and coordinated approach, emphasizing the importance of public policies aimed at promoting clean energy, sustainable transportation, and more environmentally friendly agricultural practices. The Brazilian case reveals specific difficulties, including deforestation in the Amazon, the scarcity of financial resources, and economic pressures that often prioritize economic growth over environmental concerns. The article also explores the complexities of Brazil's political and economic context, discussing the challenges of balancing economic development with environmental sustainability. Despite the ambitious goals set by the Paris Agreement, the lack of coercive mechanisms and internal political divergences represent significant barriers to the effective implementation of environmental measures in the country, requiring greater commitment and coordination between public and private sectors.

Coercivity mechanism and magnetization reversal of anisotropic La-Nd-Dy-Fe-B micron-sized films

The coercivity mechanism and magnetization reversal process of anisotropic La-Nd-Dy-Fe-B micron-sized films have been investigated. By varying the thickness of the single-layer film from 500 nm to 6 μm, the highest coercivity of 1.88 T in the film with 3 μm thickness is achieved at 300 K, due to the large dipole interaction and domain pinning effect. When the thickness is further increased to 6 μm, the coercivity decreases sharply to 1.11 T due to the microstructure and phase formation in the film. In the 6 μm multilayer film, the addition of a Ta spacer layer further enhances perpendicular magnetic anisotropy, the dipole interaction, and adjusts the phase distribution, collectively boosting the coercivity of the micron-sized film (1.63 T). As thickness of the film increases, the dominant mechanism of coercivity shifts from a pinning mechanism to a nucleation mechanism. This study contributes to the understanding of the coercivity mechanism and magnetization reversal process in La-Nd-Dy-Fe-B permanent magnet micron-sized films.

Lamellar Zr-rich phase and its influence on coercivity for Sm(CoFeCuZr)z magnets

The precipitation-hardened Sm-Co permanent magnets relied on the pinning of nanocellular structures to achieve high coercivity, and have an irreplaceable position in high-temperature applications. In this article, by employing micromagnetic simulations and magnetic domain observations, the pinning behavior of lamellar phases (Z-phase) were investigated, which has not been well understood before. The results showed that the Z-phase can serve as a strong pinning position, but due to the parallel lamellar distribution, the magnetic domain walls can move around. Additionally, the effect of Z-phase on coercivity was achieved by changing the morphology of magnetic domain walls during magnetization reversal. For attractive pinning, the coercivity was reduced by the Z-phase, while for repulsive pinning, the Z-phase increased the coercivity when γZ＜0.54γH. Our findings can provide a novel understanding of the coercivity mechanism of precipitation-hardened Sm-Co permanent magnets.

Achieving high-performance regeneration of grain boundary diffusion Nd-Fe-B sludge via an ultra-short process

The grinding sludge of grain boundary diffusion Nd-Fe-B magnet is rich in heavy rare earth and has a typical core–shell microstructure. In this work, an ultra-short process was developed to realize green, in-situ regeneration of the sludge and efficient reuse of heavy rare earth elements. The regenerated magnets showed excellent magnetic performance and good temperature stability which were fabricated after the purification of sludge, composition regulation with rare earth-rich compounds, Nd42.1FebalB0.79, NdHx, (PrNd)Hx, and sintering. Especially, the magnet prepared by using Nd42.1FebalB0.79 alloy had significant property recovery, where remanence and coercivity were restored to 12.8 kG, and 20.6 kOe, respectively, reaching 97.7 % and 162.5 % of the original magnet. The magnetization reversal behavior and the coercivity mechanism were analyzed to keep the nucleation mechanism, and the high coercivity stemmed from the repair and optimization of the grain boundary by introducing rare earth-rich alloys, the full utilization of heavy rare earth elements, and the core–shell microstructure rooted in the sludge as well.

Phase structure evolution and coercivity mechanism of high-Co containing permanent magnets

Abstract The phase structure and magnetic properties of high-Co containing permanent magnets with high thermal stability have been systematically studied in this work. It is abnormal that the coercivity of annealed samples was slightly lower than that of sintered samples, while the coercivity was usually enhanced after annealing in conventional Nd–Fe–B samples. Further analysis showed that in addition to RE2(Fe,Co)14B main phase and RE-rich grain boundary phase, there were also new Co-rich magnetic phases located in the grain boundary. During annealing, the phase structures of high-Co containing magnets were readjusted, especially the increasing Co-rich magnetic phase and emerging RE-rich particles precipitated from the main phase. Eventually, the isolated RE-rich particles would act as the pinning center of the domain wall movement in demagnetization process. It was confirmed that the coercivity of annealed high-Co containing magnets was controlled by both nucleation and pinning. Pinning mechanism can partially compensate for the weakening of magnetic isolation due to increased Co-rich magnetic phase, which explained the moderate decrease in coercivity of annealed high-Co containing magnets. The discovery of new coercivity mechanism contributed to in-depth understanding of high-Co containing magnets.

Hydro Political Relation in the Eastern Nile Basin

Abstract Hydropolitical relations have long attracted the world of academia, and hydrohegemony and counter-hydrohegemony frameworks have recently become important in analysing power relations between riparian states. However, little attention has been given to the hydrohegemonic situation of the Nile River. This study tries to analyse this status, specifically in the Eastern Nile Basin. The data, elicited through unstructured interviews from purposively selected informants, has been analysed thematically. The findings reveal that Egypt aspires to be a hegemon in the basin but is not. Despite its use of different coercive and subtle mechanisms to induce ideational or hegemonic compliance, these have not been successful: Ethiopia has not consented to or accepted Egypt’s claim over the Nile. Concomitantly, since the 1990s, Ethiopia’s position has transcended from veiled to overt contest, which anticipates a new order, challenging the monopolistic position of Egypt.

Employee ownership in China: new evidence

PurposeWith specific big-data mining worked on 61,522 firm announcements, we discovered a diverse Employee Share Ownership Plan (ESOP) model in China, called “Core-Staff-Based ESOPs.” Distinct from standard broad-based or executive-based ESOPs, these specific targeted-broad-based ESOPs require the qualification for participants, involving the participation of senior executives, directors at the middle level and any other employees that make particular contributions to firms. We take on the challenge to analyze ESOP mechanism, firm characteristics and performance in the view of organizational ecology and resource-based choice-making, and explore which factors have influenced the ESOP development in China.Design/methodology/approachWe utilize a combination of approaches including qualitative and quantitative methods, and construct the main database of 117,767 firm-quarter data.FindingsFirstly, based upon our institutional research, we find no coercive mechanisms that force all the Chinese listed firms to implement ESOPs since 2005. Secondly, our binary logistic regressions identify ESOP firms’ specific properties significantly distinct from non-ESOP firms, and draw profiles for these ESOP firms. Thirdly, our panel regression test results sustain the rational of ESOP mechanism, demonstrating that ESOPs enable Chinese firms to improve performance both in profits and their industry positions. Finally, with further quantitative tests, we find out this ESOP design’s limitations and the heterogenous effects due to China’s environments.Originality/valueThe discovery of Core-staff-based ESOPs contributes a diversity to the standard framework of ESOPs, enhances our understanding of China’s ESOP development, and provides new evidence for ESOP performance.

Synergistic influence mechanism of B-Ga content on microstructures and magnetic properties of Nd-Fe-B ribbons

To understand the influence mechanism of B and Ga content on magnetic properties of NdFeB ribbons, Nd29.89FebalGayCo5.93Bx (wt%, x = 0.80–0.98, y = 0.24–1.04) alloys were prepared and magnetic properties, phase composition, coercivity mechanism, and microstructure of these alloys were investigated systematically. The melt-spun ribbons exhibited 2:14:1 phase grains with varying grain sizes and amorphous grain boundary phases at a wheel speed of 25 m/s. By reducing the B content within a specific range, grain refinement was achieved, resulting in narrower triangular grain boundaries, more uniform and continuous thin grain boundaries. Meanwhile, further increasing the Ga content, the grain shape changes from elongated to equiaxed, and the grain size is greatly refined. However, for x = 0.89, y = 0.84 strip, the coercivity is still reduced due to the large number of directly contacted grains. Consequently, an alloy composition of Nd29.89FebalGa0.64Co5.93B0.89 yielded excellent comprehensive magnetic properties, including a remanence of 8.5 kGs and a coercivity of 18.01 kOe. The corresponding magnetic properties enhancement mechanism is further discussed.

High-coercivity nanocrystalline Nd-Fe-B powder regenerated from sludge via in-situ mechanochemical approach

The regeneration of Nd-Fe-B sludge is of great practical significance for achieving the sustainable development and recycling of rare earth elements. In this study, the in-situ regeneration of sludge was realized at a lower temperature of 850 °C via the mechanochemical approach based on ball-milling and Ca-reduction diffusion. Single-phase nanocrystalline magnetic powders with high coercivity were prepared by regulating the experimental parameters and rare earth elements. The grain size of Nd-Fe-B powder obtained by 5 wt% TbHx addition was 68.1 nm, with a high coercivity of 18.38 kOe. After purification and dehydrogenation, the coercivity was 6.68 kOe, and the coercivity mechanism was controlled by reverse magnetic domain nucleation. The low temperature in this study significantly reduced the energy consumption for the calcium reduction regeneration of sludge. It facilitated the preparation of nanocrystalline Nd-Fe-B powders with high coercivity, offering a new idea for recycling Nd-Fe-B sludge.

Optimizing the Sintering Conditions of (Fe,Co)1.95(P,Si) Compounds for Permanent Magnet Applications.

(Fe,Co)2(P,Si) quaternary compounds combine large uniaxial magnetocrystalline anisotropy, significant saturation magnetization and tunable Curie temperature, making them attractive for permanent magnet applications. Single crystals or conventionally prepared bulk polycrystalline (Fe,Co)2(P,Si) samples do not, however, show a significant coercivity. Here, after a ball-milling stage of elemental precursors, we optimize the sintering temperature and duration during the solid-state synthesis of bulk Fe1.85Co0.1P0.8Si0.2 compounds so as to obtain coercivity in bulk samples. We pay special attention to shortening the heat treatment in order to limit grain growth. Powder X-ray diffraction experiments demonstrate that a sintering of a few minutes is sufficient to form the desired Fe2P-type hexagonal structure with limited secondary-phase content (~5 wt.%). Coercivity is achieved in bulk Fe1.85Co0.1P0.8Si0.2 quaternary compounds by shortening the heat treatment. Surprisingly, the largest coercivities are observed in the samples presenting large amounts of secondary-phase content (>5 wt.%). In addition to the shape of the virgin magnetization curve, this may indicate a dominant wall-pining coercivity mechanism. Despite a tenfold improvement of the coercive fields for bulk samples, the achieved performances remain modest (HC ≈ 0.6 kOe at room temperature). These results nonetheless establish a benchmark for future developments of (Fe,Co)2(P,Si) compounds as permanent magnets.

Elevated temperature magnetic microstructures and demagnetization mechanism for grain boundary diffused dual-main-phase (Nd, Ce)-Fe-B magnets

The combination of dual-main-phase (DMP) (Nd, Ce)-Fe-B magnets and grain boundary diffusion process (GBDP) is currently a research topic for obtaining high-cost performance materials in rare earth permanent magnet fields. The novel structural features of GBDP (Nd, Ce)-Fe-B magnets give a version of different domain reversal processes from those of non-diffused magnets. In this work, the in-situ magnetic domain evolution of the DMP magnets was observed at elevated temperatures, and the temperature demagnetization and coercivity mechanism of the GBDP dual-main-phase (Nd, Ce)-Fe-B magnets are discussed. The results show that the shell composition of different types of grains in DMP magnets is similar, while the magnetic microstructure results indicate the Ce-rich grains tend to demagnetize first. Dy-rich shell with a high anisotropic field caused by GBDP leads to an increase in the nucleation field, which enhances the coercivity. It is found that much more grains exhibit single domain characteristics in the remanent state for GBDP dual-main-phase (Nd, Ce)-Fe-B magnets. In addition, the grains that undergo demagnetization first are Ce-rich or Nd-rich grains, which is different from that of non-diffused magnets. These results were not found in previous studies but can be intuitively characterized from the perspective of magnetic domains in this work, providing a new perspective and understanding of the performance improvement of magnetic materials.