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Rare earth oxides with a trivalent nature play a pivotal role in reinforcing the magneto-optical attributes of spinel ferrite nanoparticles by replacing Fe3+ ions. In this study, rare earth Gd oxide doped with CoFe2O4 NPs with a composition of Co1+xGdxFe2-2xO4 (x = 0, 0.05, 0.10, and 0.15) were synthesized using sol-gel auto-combustion. The outcome of Gd cations on the physical, magneto-optical and electrical characteristics of the cobalt ferrite NPs were reported. X-ray diffraction (XRD), and Fourier transform infrared (FTIR) investigations confirmed the single-phase cubic crystalline nature and metal ion stretching in the cobalt ferrite synthesized samples. Decreasing drift in the average crystallite and grain sizes (estimated from the XRD patterns and SEM micrographs) and magnetic saturation ( M s ) were examined with the increasing content of Gd oxide and Co ions in the CoFe2O4 NPs. The optical bandgap of the synthesized samples explains the semiconducting nature of the prepared NPs due to the presence of an E g from 2.13 eV to 2.45 eV in the semiconductor region. The electrical properties of the co-doped samples exhibit a conducting trend in the presence of Gd3+ ions with the increase of temperature from 298 K to 973 K. DC measurements of the synthesized NPs demonstrated DC conductivity values from 0.1087 S/cm to 0.2676 S/cm at 973 K.

Interfacial disorder is a general method to change the metal-oxygen compatibility and carrier density of heterostructure materials for ionic transport modulation. Herein, to enable high proton conduction, a semiconductor heterostructure based on spinel ZnFe2O4 (ZFO) and fluorite CeO2 is developed and investigated in terms of structural characterization, first principle calculation, and electrochemical performance. Particular attentions are paid to the interfacial disordering and heterojunction effects of the material. Results show that the heterostructure induces a disordered oxygen region at the hetero-interface of ZFO-CeO2 by dislocating oxygen atoms, leading to fast proton transport. As a result, the ZFO-CeO2 exhibits a high proton conductivity of 0.21 S/cm and promising fuel cell power output of 1070 mW/cm2 at 510 ℃. Based upon these findings, a new mechanism is proposed to interpret the diffusion and acceleration of protons in ZFO-CeO2. Our study provides a new strategy to customize semiconductor heterostructure to enable fast proton conduction.

Interfacial atomic configuration between dual-metal active species and nitrogen-carbon substrates is of great importance for improving the intrinsic activity of catalysts toward oxygen reduction reaction (ORR). Thus, from the atomic-scale engineering we develop a high intrinsic activity ORR catalyst in terms of incorporating atomically dispersed dual Fe centers (single Fe atoms and ultra-small Fe atomic clusters) into bamboo-like N-doped carbon nanotubes. Benefiting from atomically dispersed dual-Fe centers on the atomic interface of Fe-Nx/carbon nanotubes, the fabricated dual Fe centers catalyst exhibits an extremely high ORR activity (Eonset = 1.006 V; E1/2 = 0.90 V), beyond state-of-the-art Pt/C. Remarkably, this catalyst also shows a superior kinetic current density of 19.690 mA·cm−2, which is 7 times that of state-of-the-art Pt/C. Additionally, based on the excellent catalyst, the primary Zn-air battery reveals a high power density up to 137 mW·cm−2 and sufficient potential cycling stability (at least 25 h). Undoubtedly, given the unique structure-activity relationship of dual-Fe active species and metal-nitrogen-carbon substrates, the catalyst will show great prospects in highly efficient electrochemical energy conversion devices.

In this paper, we study the longtime dynamics for the weakly damped wave equation with quintic non-linearity in a bounded smooth domain of $\mathbb{R}^3.$ Based on the Strichartz estimates for the case of bounded domains, we establish the existence of a strong global attractor in the phase space $H^2(\Omega)\cap H^1_0(\Omega)\times H^1_0(\Omega)$. Moreover, the finite fractal dimension of the attractor is also shown with the help of the quasi-stable estimation., Comment: 18 pages

The synchronization of complex dynamic systems is a hot topic in scientific research. Thus, this paper focuses on the synchronization of two different laser systems and studies the multiple-dynamics behavior of two coupling lasers synchronizing with that of another laser, and present a physical model of the multiple-dynamics synchronization. Two routes to chaos after bifurcation from two stable states are illustrated by controlling one current of the two coupling lasers while the two coupling lasers are found to produce great nonlinear dynamics behaviors via their bifurcation diagrams. And this paper discusses the detailedly multiple-dynamics distribution of the two coupling lasers, where there is a stable-state region, a single-period region, a quasi-period region, and a chaotic region. Our work performs how multiple-dynamics of the two coupling lasers synchronize with that of another laser by controlling one current of the two coupling lasers. Then, multiple dynamics behaviors of the two coupling lasers synchronizations are obtained with that of another laser, such as a single-period synchronization, a period-doubling synchronization, a period-4 synchronization, a period-5 synchronization, other quasi-period synchronization, and a chaotic synchronization. The obtained results are of great significance to study laser physics, optics, synchronizations of two optical dynamic systems, a chaotic laser, and its application.

There are great challenges to develop and fabricate a high performance, low-cost and stable non-platinum catalyst for hydrogen evolution reaction (HER). In our study, we firstly developed a simple method to successfully fabricate a new MoS2/NiCo2S4 heterostructure by a two-step hydrothermal method, and studied the HER property of MoS2/NiCo2S4, where the as-prepared NiCo-layered double hydroxide (NiCo-LDH) was used as the precursor of NiCo2S4. Benefitting from the prominent synergistic effect between NiCo2S4 and MoS2, MoS2 provided massive catalytic active edge sites, and NiCo2S4 enhanced the conductivity of the composite. As a result, the MoS2/NiCo2S4 showed excellent HER catalytic activity, with a current of 10 mA cm−2 at overpotential of 94 mV for HER and a low Tafel slope of 46 mV dec−1, and good cycling stability in Alkaline Media. As well as, our work offered one promising high active and stable non-platinum catalyst for overall water splitting.

Reducing the operating temperature of Solid Oxide Fuel Cells (SOFCs) to 300–600 °C is a great challenge for the development of SOFC. Among the extensive research and development (R&D) efforts that have been done on lowering the operating temperature of SOFCs, nanomaterials have played a critical role in improving ion transportation in electrolytes and facilitating electrochemical catalyzation of the electrodes. This work reviews recent progress in lowering the temperature of SOFCs by using semiconductor-ionic conductor nanomaterial, which is typically a composition of semiconductor and ionic conductor, as a membrane. The historical development, as well as the working mechanism of semiconductor-ionic membrane fuel cell (SIMFC), is discussed. Besides, the development in the application of nanostructured pure ionic conductors, semiconductors, and nanocomposites of semiconductors and ionic conductors as the membrane is highlighted. The method of using nano-structured semiconductor-ionic conductors as a membrane has been proved to successfully exhibit a significant enhancement in the ionic conductivity and power density of SOFCs at low temperatures and provides a new way to develop low-temperature SOFCs.

Diffusion MRI (DMRI) plays an essential role in diagnosing brain disorders related to white matter abnormalities. However, it suffers from heavy noise, which restricts its quantitative analysis. The total variance (TV) regularization is an effective noise reduction technique that penalizes noise-induced variances. However, existing TV-based denoising methods only focus on the spatial domain, overlooking that DMRI data lives in a combined spatioangular domain. It eventually results in an unsatisfactory noise reduction effect. To resolve this issue, we propose to remove the noise in DMRI using graph total variance (GTV) in the spatioangular domain. Expressly, we first represent the DMRI data using a graph, which encodes the geometric information of sampling points in the spatioangular domain. We then perform effective noise reduction using the powerful GTV regularization, which penalizes the noise-induced variances on the graph. GTV effectively resolves the limitation in existing methods, which only rely on spatial information for removing the noise. Extensive experiments on synthetic and real DMRI data demonstrate that GTV can remove the noise effectively and outperforms state-of-the-art methods.

In this paper, we first establish a criterion based on contractive function for the existence of polynomial attractors. This criterion only involves some rather weak compactness associated with the repeated limit inferior and requires no compactness, which makes it suitable for critical cases. Then by this abstract theorem, we verify the existence of a polynomial attractor and estimate its attractive speed for the wave equation with nonlocal weak damping, anti-damping and critical nonlinearity., Comment: arXiv admin note: text overlap with arXiv:2108.07410

We present a giant chaotic network having the characteristics of a giant nonlinear chaotic dynamic system. Based on two space coupling Lorentz systems with different parameters, a hyper-chaotic energy source is used to drive each chaotic system in two-way. Which results in a parallel series network with two ways. Each node in two-way of network is a highly nonlinear dynamic system and has the chaotic characteristics, where each node of network is a chaotic system. Then, we define such network as a giant chaotic network or a giant nonlinear chaotic dynamic system. We find many hyper-chaotic states and their hyper-chaotic regions via a Lyapunov exponents diagram. We also give a bifurcation diagram to illustrate roughly dynamic behavior of the two coupling Lorentz system from a stable state to a single-periodic state, a multi-periodic state, a chaotic state and a hyper-chaotic state by shifting some parameter. And we discuss all kinds of state synchronization difference via the maximal LES. The network can be found to obtain a hyper-chaotic synchronization and all kinds of state synchronizations in all nodes in two-way. Our research result is of great significance to the research of artificial network, complex system and artificial intelligence.