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High-frequency soft magnetic ferrite ceramics are desired in miniaturized and efficient power electronics but remain extremely challenging to deploy on account of the power loss (Pcv) at megahertz frequencies. Here, we prepared NiCuZn ferrite with superior high-frequency properties by V2O5 and Bi2O3 synergistic doping, which proves to be a potent pathway to reduce Pcv of the ferrite at megahertz frequencies. The sample doped with 800 ppm V2O5 and 800 ppm Bi2O3 yielded the most optimized magnetic properties with a Pcv of 113 kW/m3 (10 MHz, 5 mT, 25 °C), an initial permeability (μi) of 89, and a saturation induction (Bs) of 340 mT, which is at the forefront of the reported results. These outstanding properties are closely related to the notable grain boundary structure, which features a new type of nano-Bi2Fe4O9 phase around ferrite grains and a Ca/Si/V/O amorphous layer. Our results indicate great strides in correlating the grain boundary structure with multiple-ion doping and set the scene for the developing high-frequency soft magnet ferrites.

Dzyaloshinskii-Moriya interaction (DMI), one of antisymmetric exchanges, originates from the combination of low structural symmetry and large spin-orbit coupling and favors magnetization rotations with fixed chirality. Herein, this work reports a DMI-like behavior in permalloy via coupled vortices in confined structures. Under the in-plane magnetic fields, continuous reversals of different coupled vortices are directly observed by in situ Lorentz transmission electron microscopy, and reproduced by complementary micromagnetic simulations. The statistical results show that coupled vortices with opposite chirality appear more frequently with the frequency up to about 60%. Such an asymmetric phenomenon mainly arises from a DMI-like behavior, associated with the increased total energy difference between different ground-state coupled vortices. Moreover, in the reversal process, the junction between disks accelerates the annihilation of vortices moving toward it and is also the starting point of vortex nucleation. These results provide an effective method to generate a DMI-like behavior in magnetic systems with symmetry breaking surface and benefit the future development of vortex-based spintronic devices.

A facile oxidation strategy is proposed to in situ grow a hydrophobic, thin and uniform triplex surface coating on Nd–Fe–B, which ensures outstanding anti-corrosion performance, accompanied with synergistic magnetic and mechanical performance.

MnZn soft magnetic ferrites have been widely utilized in power electronics, owing to the combined merits of high permeability and low energy loss. However, their deployment would result in a drastic increase in power dissipation at >3 MHz, thus limiting the scope extent of miniaturization, together with their efficiency. Here, we report a high-performance MnZn ferrite by doping multiple ions (La, Ti, Si, Ca) at grain boundaries, achieving the most optimized power loss of 267 kW/m3 at 5 MHz (10 m T, 100 °C) and initial permeability of 644, which is much better than the previously reported results and commercial products. Such an improvement is attributed to weakened magnetic exchange coupling at grain-boundary regions, associated with a significant transition from the multi- to mono-domain structures, originating physically from large crystallographic mis-orientations (>25°). The present study bears important significance in understanding the intrinsic correlation between the crystallographic mis-orientation and magnetic domain structure, and provides an alternative way for optimizing high-frequency soft magnetic ferrites.

MnZn power ferrites are technologically important for miniaturization and efficiency of electronic devices. It is of practical significance to obtain high working frequency and temperature in the MnZn ferrites. In this study, MnZn ferrites capable of working above 1 MHz and 80 °C have been successfully prepared by Nb2O5 and TiO2 doping. Nb2O5 promotes the densification process during sintering and exists as a resistive layer in the grain boundary region, leading to improved permeability and power losses. TiO2 doping results in the formation of localized Ti4+-Fe2+ pairs and offers extra cation vacancies for Nb5+ diffusion, which further enhances the effect of Nb2O5. The sample doped with 250 ppm of Nb2O5 and 2500 ppm of TiO2 presents optimal magnetic properties with the lowest power loss value of 394 kW/m3 at 1 MHz and 80 °C , along with an initial permeability of 1510, thus, serving as a good candidate for MHz, high-temperature and high-permeability power applications.

Low-dimensional soft magnetic materials are technologically important for miniaturization of magnetic devices. It is, however, challenging to maintain ferromagnetic response in nanosized magnetic material. In this work, ultrafine FeCo nanoparticles have been prepared by reactive pulsed laser deposition, which can be exchange coupled through ultrathin dielectric shells, even though their diameters are far below the superparamagnetic blocking limit. This unique core/shell structure guarantees ferromagnetic coupling and insulation of neighboring magnetic nanoparticles simultaneously. The nanoparticle film exhibits large saturation magnetization of 1.13 T, high electrical resistivity of 4200 μΩ·cm, maximum permeability of 120, a cutoff frequency of 1.7 GHz, and it is a promising material for microwave application.

The rapid advancement of modern electronic technology requires MnZn ferrites capable of handling high-frequency signals, offering very low power loss and reasonably high permeability. MnZn ferrites were developed by using the conventional ceramic processing technique and the effects of Co2O3 and SnO2 doping on high-frequency magnetic properties were investigated. Co2O3 and SnO2 co-doping resulted in a sharp decrease of eddy-current loss and residual loss of the MnZn ferrites at 3–5 MHz and improved the temperature characteristics at 20–120 °C. The minimum power losses at 20 °C, 10 mT for 3 MHz and 5 MHz were 20 kW/m3 and 81 kW/m3, while the power losses at 100 °C, 10 mT for 3 MHz and 5 MHz were 60 kW/m3 and 205 kW/m3 respectively. The optimal saturation magnetic flux density and initial permeability were 480 mT and 675 respectively. The cut-off frequency of the sample was 12 MHz, establishing it as an ideal material for high-frequency applications.

The Fe–Si–B amorphous ribbons with various CO ventilation amount were prepared by planar-flow melt spinning method. The effect of CO gas on surface quality, magnetic properties and core loss of amorphous ribbons were investigated. With the increasing CO ventilation, the wheel side surface roughness, average air pocket size and air pocket quality decrease, the ribbon grows thicker, but air side surface roughness remains almost no changes. The three samples have reached to a fully amorphous structure. Meanwhile the diffraction angle corresponding the maximum intensity of each broad diffraction peak decrease slightly with increasing CO ventilation. There is no significant differences in the onset temperate of second exothermic peak (Tx2) and the crystallization peak temperature (Tp1 and Tp2) among the amorphous ribbons prepared with various CO ventilation, but the onset temperate of first exothermic peak (Tx1) increases slightly with the increasing CO ventilation. The room temperature hysteresis loops of amorphous ribbons show that surface quality have significant effect on magnetic properties. The coercivity (Hc), core loss (P1.35/50), magnetic polarization (B80) and permeability (µ) among the ribbons are improved with better surface quality, though the saturation magnetic flux density almost keeps same. Core loss are separated by the scaling theory, and experiment dates show a good agreement with the predicted data. Thus the scaling theory is suitable for Fe–Si–B amorphous alloys. The surface quality has more significant effect on hysteresis losses than eddy current loss at low frequency.

Two-step post-sinter annealing (PSA) treatment, due to its universal applicability, has been one of the most effective strategies for enhancing the coercivity of Nd-Fe-B sintered magnets. Here we report a peculiar phenomenon that the as-sintered multi-main-phase (MMP) Nd-La-Ce-Fe-B magnet exhibits the highest reported to date coercivity of 13.0 kOe upon 25 wt% La-Ce substituting for Nd, combined with Br = 13.12 kG, and (BH)max = 41.67 MGOe. Further annealing cannot enhance the coercivity whereas the remanence and energy product are drastically lowered, i.e. to 11.0 kOe, 12.57 kG, and 38.71 MGOe after two-step PSA, being remarkably different from the conventional Nd-Fe-B. Microstructural analysis reveals that the as-sintered Nd-La-Ce-Fe-B magnet with coexisting REFe2 (Fd 3 ¯ m) and RE-rich (Fm 3 ¯ m) intergranular phases possesses continuous GB layer isolating adjacent ferromagnetic grains. Hence the beneficial role of PSA on modifying the microstructure and strengthening the coercivity is tiny. Additionally, high-temperature PSA destroys the initial chemical heterogeneity of MMP magnets, leading to the formation of REs homogeneously distributed grains and resultant reduction of the intrinsic magnetic properties. As evidenced by in-situ Lorentz TEM characterization, PSA sample with reduced chemical gradient exhibits quick domain wall motion, compared to the as-sintered one with basically unchanged magnetic domain structure upon the same applied field. The proof-of-principle micromagnetic simulation further confirms that retaining the inhomogeneous La/Ce/Nd distribution is essential to suppress the magnetic dilution effect. These findings demonstrate the realistic prospect of skipping PSA treatment in MMP magnets, which can not only reduce the production process and cost, but also delight the scenario for designing high-performance 2:14:1-type sintered magnets based on abundant La/Ce.

A hybrid cloud model for diabetes home-based care : a case study for perceived future feasibility

Influences of (Nd, Pr)H x additives on the microstructure and mechanical properties of Nd–Pr–Ce–Fe–B sintered magnets have been investigated. The results show that both the fracture toughness and bending strength exhibit a monotonically increasing trend with raised (Nd, Pr)H x incorporation. The (Nd, Pr)H x powders transform into metallic Nd/Pr with high reactivity upon dehydrogenation, increasing the volume fraction of rare earth-rich intergranular phase, and promoting the formation of thick and continuous grain boundary (GB) layer surrounding the RE2Fe14B matrix phase grains. Besides, the hydrogen desorption behavior also demonstrates that the excessive hydrogen introduced by (Nd, Pr)H x additives can be completely released upon high-temperature sintering. As a result, the crack propagation along the thick GBs is suppressed, giving rise to the substantially enhanced mechanical performance of bulk magnets. This paper suggests that the Nd–Pr–Ce–Fe–B permanent magnet with (Nd, Pr)H x incorporation satisfies the constraints of cost, magnetic, and mechanical properties simultaneously, thereby possessing competitive advantages for mass production.

Single-phase cobalt ferrite nanoparticles were synthesized by coprecipitation method and annealed at different temperatures. The structural, dielectric and magnetic properties were investigated, which showed an obvious dependence on annealing temperature. The average crystallite size increased from 20 to 60 nm with increase of annealing temperature. Meanwhile, the shape of nanoparticles also changed from spherical to octahedron and then cubic. Dielectric constant showed dispersion behavior and decreased with increasing annealing temperature, while the relaxation peaks observed in dielectric loss were shifted to lower frequencies. The ac conductivity originates from Polaron hopping which decreased with increase of crystallite size (less surface area and defect density) due to higher annealing temperature. The saturation magnetization increased from 59 to 81 emu/g and coercivity dropped from 1316 to 428 Oe with the increase of particle size.

Inferior intrinsic magnetic properties of (La/Ce)2Fe14B to Nd2Fe14B compound pose a big challenge for the Nd-La-Ce-Fe-B sintered magnets to provide an equivalent performance to the commercial Nd-Fe-B ones. To suppress the magnetic dilution, La/Ce distributions within 2:14:1 phase are intentionally tailored in the present work. At the same La-Ce substitution level of 12 wt%, the coercivity has been substantially increased to 1.36 T by constructing the coexisting Nd-rich shell @ La/Ce-rich core and La/Ce-rich shell @ Nd-rich core morphologies, compared to the La/Ce homogenously distributed magnet (0.76 T) and the one with singular Nd-rich core surrounded by La/Ce-rich shell (0.82 T). This is attributed to combined effects of magnetically hardening Nd-rich shell in suppressing the reversal domain nucleation, and continuous grain boundary layer in reducing the short-range exchange coupling between adjacent ferromagnetic grains. It may act as part of endeavors to promote the Nd-La-Ce-Fe-B sintered magnets for commercial application.

Health data integration enables a collaborative utilization of data across different systems. It not only provides a comprehensive view of a patient’s health but can also potentially cope with challenges faced by the current healthcare system. In this literature review, we investigated the existing work on heterogeneous health data integration as well as the methods of utilizing the integrated health data. Our search was narrowed down to 32 articles for analysis. The integration approaches in the reviewed articles were classified into three classifications, and the utilization approaches were classified into five classifications. The topic of health data integration is still under debate and problems are far from being resolved. This review suggests the need for a more efficient way to invoke the various services for aggregating health data, as well as a more effective way to integrate the aggregated health data for supporting collaborative utilization. We have found that the combination of Web Application Programming Interface and Semantic Web technologies has the potential to cope with the challenges based on our analysis of the review result. open access

To balance the utilization of rare earth (RE) resource, abundant La has been incorporated into the Nd-Fe-B sintered magnets via the binary main phase (BMP) approach. Microstructure and magnetic properties of the Nd-La-Fe-B BMP magnets with increasing La substitution from 0 to 45 wt% were investigated. The results show that RE-rich intergranular phase with high oxygen content forms easily in the triple junction region for the La-substituted magnets. Those hcp-RE2O3 precipitates exhibit poor wettability with the matrix phase, leading to the direct exchange coupling of adjacent grains. As a result, the coercivity of Nd-La-Fe-B BMP magnets is dramatically reduced. Fortunately, the remanence can be maintained at a high level, ascribing to the inhomogeneous RE distributions among the grains (core-shell morphology), and the stable tetragonal phase after high-temperature sintering. With 27 wt% La substitution for Nd in the BMP magnet, the remanence decreases from 13.15 to 13.01 kGs by merely 1.06%. This work suggests that if one can optimize the microstructure by constructing magnetically isolated grains, low-cost Nd-La-Fe-B BMP magnets can be promising candidates for mass production.

SnO 2 films exhibiting room temperature ferromagnetism (RTFM) have been prepared on Si (001) by pulsed laser deposition. The saturation magnetization (M s ) of the films experiences a decreasing trend followed by increasing with the growth temperature increased from RT to 400 ℃. The growth temperature affects both the concentration and the location of the oxygen vacancies as the origin of the RTFM. With lower growth temperatures ( O + ) in the inner film are the origin of the magnetism in SnO 2 films.

Knowledge sharing has become an important issue that challenges the efficient healthcare delivery in eHealth system. It also rises as one of the mostdemanding applications with reference to dynamic interactivities among various healthcare actors (e.g. doctors, nurses, patients, relatives of patients). Inthis paper, we suggest an activity theory based ontology model to represent various healthcare actors. The goal of the suggested model is to enhance inte-ractivities among these healthcare actors for conducting more efficient knowledge sharing, which helps to design eHealth system. To validate the feasibilityof suggested ontology model, three typical use cases are further studied. A questionnaire based survey is carried out and the corresponding survey resultsare reported, together with the detailed discussions. open access

We present a potent pathway, (Nd, Pr)Hx and Cu grain boundary engineering, to tackle the trade-offs between coercivity, remanence and corrosion resistance of Nd-Ce-Fe-B sintered magnets. Concurrent improvements of magnetic and corrosive properties are achieved in 25 wt% Ce-substituted magnet depending on the (Nd, Pr)Hx/Cu ratio. A representative 8:2 ratio yields room-temperature magnetic performance (Hcj = 14.1 kOe, Br = 12.88 kG, (BH)max = 39.4 MGOe) equivalent to that of N40M commercial-grade Nd-Fe-B, as well as superb thermal stability (coercivity coefficient |β| of 0.55%/K within the 293-413 K interval) and electrochemical resistance. These outstanding properties are closely correlated to the three notable microstructural characteristics, including (1) an increasing fraction of the REFe2 phase with raised Cu content, (2) the occurrence of a new-type Cu-dissolved REFe2 phase with higher Nd/Pr and lower Ce content than conventional 1:2 phase, and (3) a Cu-dissolved RE-rich phase with deficient Fe. Above structural and chemical features are discussed on the basis of experimental studies, which allow for better continuity of non-ferromagnetic grain boundary phase and higher chemical stability of intergranular regions, thus enabling a good compatibility of magnetic and anti-corrosive performance. Our exploration of (Nd, Pr)Hx and Cu synergy may pave a novel way for developing high-figure-of-merit Nd-Ce-Fe-B permanent magnets that rival the commercial Nd-Fe-B counterpart.

The utilization of Web services is becoming a human labor consuming work as the rapid growth of Web. The semantic annotated service description can support more automatic ways on tasks such as service discovery, invocation and composition. But the adoption of existed Semantic Web Services solutions is hindering by their overly complexity and high expertise demand. In this paper we propose a highly lightweight and non-intrusive method to enrich the REST Web service resources with semantic annotations to support a more autonomous Web service utilization and generic client service interaction. It is achieved by turning the service description into a semantic resource graph represented in RDF, with the added tag based semantic annotation and a small vocabulary. The method is implemented with the popular OpenAPI service description format, and illustrated by a simple use case example.

Various health Web services host a huge amount of health data about patients. The heterogeneity of the services hinders the collaborative utilization of these health data, which can provide a valuable support for the self-management of chronic diseases. The combination of REST Web services and Semantic Web technologies has proven to be a viable approach to address the problem. This paper proposes a method to add semantic annotations to the REST Web services. The service descriptions and the resource representations with semantic annotations can be transformed into a resource graph. It integrates health data from different services, and can link to the health-domain ontologies and Linked Open Health Data to support health management and imaginative applications. The feasibility of out method is demonstrated by realizing with OpenAPI service description and JSON-LD representation in an example use case. open access