Accepted
, , Received Date: 2025-02-06
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Diffusion-weighted magnetic resonance imaging (DWI) holds significant value in neuroscience and clinical disease diagnosis. The most commonly used single-shot echo-planar imaging (EPI) for DWI is affected by static magnetic field (B0) inhomogeneity and T2/T2* decay, leading to geometric distortion, low signal-to-noise ratio (SNR), etc. To solve these problems, researchers have developed more advanced high-resolution diffusion MRI techniques. This article comprehensively reviews these imaging methods. In the context of echo-planar imaging (EPI), this review covers multi-shot EPI-based DWI techniques, including readout-segmented EPI (RS-EPI), interleaved EPI (iEPI), point spread function-encoded EPI (PSF-EPI), and echo-planar time-resolved imaging (EPTI). These methods effectively reduce or eliminate geometric distortions while improving SNR and spatial resolution. Additionally, the combination of multi-shot EPI with simultaneous multi-slice (SMS) acquisition can shorten scan time, which is also briefly discussed in this article. Compared with EPI, spiral imaging offers higher SNR and sampling efficiency but is more sensitive to B0 inhomogeneity. In the spiral imaging section, we review single-shot spiral DWI and multi-shot spiral DWI, as well as their integration with SMS techniques. This article emphasizes the concepts, acquisition strategies, and reconstruction methods of these imaging techniques. Finally, we discuss the challenges and future directions of high-resolution diffusion imaging, including 3D DWI, body DWI, magnetic field probes, ultra-high gradient systems, and ultra-high-field MRI systems.
, , Received Date: 2025-03-15
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The laser energy deposition coefficient, the electron thermal conduction coefficient, and the resistivity are three important physical quantities in plasma physics. For a multi-ion-component plasma, considering only the collisional interaction between electrons and ions, starting from the kinetic equation in the Fokker-Planck approximation, and using multi-timescale method, a unified derivation of the laser energy deposition coefficient, electron thermal conduction coefficient, and resistivity in the plasma is presented.
, , Received Date: 2025-03-24
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, , Received Date: 2025-03-04
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Quantum Sensing exploits quantum resources of well-controlled quantum systems to measure small signals with high sensitivity, and has great potential for both fundamental science and concrete applications. Interacting quantum systems have attracted growing interest in the field of precision measurement, owing to their potential to generate quantum-correlated states and to exhibit rich many-body dynamics. These features provide a novel avenue for exploiting quantum resources in sensing applications. While previous studies have demonstrated enhanced sensitivity using such systems, they have primarily focused on measuring a single physical quantity. The challenge of realizing simultaneous, high-precision measurements of multiple physical parameters using interacting quantum systems remains largely unexplored in experiments. In this study, we demonstrate a first realisation of interaction-based multiparameter sensing with the use of strongly interacting nuclear spins under ultra-low magnetic field conditions. We find that, as the interaction strength among nuclear spins becomes significantly larger than their Larmor frequencies, a different regime emerges where the strongly interacting spins can be simultaneously sensitive to all components of a multidimensional field, such as a three-dimensional magnetic field. Moreover, we observe that the strong interactions between nuclear spins can increase their quantum coherence times as long as several seconds, leading to enhanced measurement precision. Our sensor successfully achieves precision measurement of three-dimensional vector magnetic fields with a field sensitivity reaching the order of 10–11 T and an angular resolution as high as 0.2 rad. Crucially, this approach eliminates the need for external reference fields, thereby avoiding calibration errors and technical noise commonly encountered in traditional magnetometry. Experimental optimization further boosts the sensitivity of the interacting spin-based sensor by up to five orders of magnitude compared to non-interacting or classical schemes. These results demonstrate the significant potential of interacting spin systems as a powerful platform for high-precision, multi-parameter quantum sensing. The techniques developed here pave the way for a new generation of quantum sensors that leverage intrinsic spin interactions to surpass conventional sensitivity limits, offering a promising route toward ultra-sensitive, calibration-free magnetometry in complex environments.
, , Received Date: 2025-02-14
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, , Received Date: 2025-03-06
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Magnetic high-entropy alloy (HEA) has certain application prospects in the fields of energy conversion, hysteresis motor, electromagnetic control mechanism and others. In this study, AlCoCrCuFeNi HEA is prepared by selective laser melting (SLM) with different process parameters, and the phase composition, microstructure, magnetic properties and micromechanical behavior are studied systematically. The results show that the SLMed alloy mainly consists of a BCC matrix phase with a small quantity of approximately spherical FCC precipitated nanophase. The nanohardness decreases with the increase of laser power and fluctuates in a certain range with the change of scanning speed, but the whole sample shows excellent micromechanical properties. Besides, it is found that the room-temperature nanoindentation creep deformation mechanism of AlCoCrCuFeNi HEAs is mainly controlled by dislocation motion, which is different from the results given by the traditional classical creep theory. Both of SLMed alloys exhibit typical semi-hard magnetic properties. The saturation magnetization is affected slightly by the SLM process parameters and remains at about 43 A·m2/kg because all samples have a similar quantity of ferromagnetic elements (Fe,Co and Ni). However, the coercivity increases from 1.72 to 2.71 kA/m with the increase of laser power (P), and decreases from 2.37 to 1.98 kA/m with the increase of scanning speed (v), which can be attributed to the different effects of porosity and internal stress on the pinning of domain walls under different process parameters (P and v). This work provides a theoretical basis and experimental direction for further studying the optimization of comprehensive magnetic properties and the room temperature creep mechanism of SLMed high-entropy alloy.
, , Received Date: 2025-03-23
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, , Received Date: 2025-01-16
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,
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In recent years, the development of attosecond extreme ultraviolet (XUV) pulse generation and advanced spectroscopic techniques has provided powerful tools for investigating electron dynamics. Studies on the attosecond timescale enable real-time tracking of electronic motion in atoms and molecules, allowing the measurement of electron wave packet evolution and quantum characteristics, which are crucial for revealing complex dynamical processes within atomic and molecular systems. High-resolution photoelectron interferometers based on attosecond XUV pulse trains have played an essential role in a wide range of applications, owing to their unique combination of high energy and temporal resolution. These include the characterization of attosecond pulse trains (APT), the measurement of photoionization time delays in atoms and molecules, quantum state reconstruction of photoelectrons, and laser-induced electronic interference phenomena. By integrating attosecond temporal resolution with millielectronvolt level energy resolution, high-resolution photoelectron interferometric spectroscopy has emerged as a key technique for probing ultrafast dynamics and quantum state characterization. This review systematically summarizes recent advances in high-resolution attosecond photoelectron interferometry, with a focus on the experimental approaches and spectroscopic techniques required to access electron dynamics on the attosecond scale. These include the generation of narrowband attosecond XUV pulse trains, attosecond-stable Mach-Zehnder interferometers, high-energy resolution time-of-flight electron spectrometers, and quantum interference-based measurement schemes such as RABBIT and KRAKEN. The article discusses in detail the reconstruction of attosecond pulse sequences, shell-resolved photoionization time delay measurements in atoms, spectral phase evolution in Fano resonances, tomographic reconstruction of photoelectron density matrices on attosecond timescales, and control experiments of laser-induced electronic dynamic interference effects. Through the analysis of recent studies, we demonstrate the powerful potential of attosecond high-energy resolution photoelectron interferometry in tracking ultrafast electron dynamics. Finally, the prospects of attosecond photoelectron spectroscopy in ultrafast dynamics and coherent manipulation of quantum systems are discussed.
,
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To improve the thermionic emission performance of the rare-earth refractory yttrium salt cathode used in the magnetron, the influence of Sc2O3 doping on its thermionic emission properties was explored. Cathodes were fabricated by incorporating different weight percentages of Sc2O3 into the rare-earth refractory yttrium salt matrix, and their thermionic emission properties were systematically evaluated. The experimental findings revealed that the doping of Sc2O3 significantly enhances the thermionic emission capability of the cathode. Notably, a doping concentration of 3wt% Sc2O3 yielded the most pronounced improvement in emission performance. The 3wt% Sc2O3-doped cathode could achieve a thermionic emission current density of 3.85A/cm2 under a 300 V anode voltage at 1600℃. In contrast, the undoped cathode supplied a current density of merely 1.66A/cm2 under identical conditions, demonstrating a 132% enhancement in thermionic emission efficiency with 3wt% Sc2O3 doping. Utilizing the Richardson line method coupled with data-fitting algorithms, the absolute zero work functions for undoped and Sc2O3-doped cathodes (3wt%, 7wt%, and 11wt%) were determined to be 1.42, 0.93, 0.98, and 1.11 eV, respectively. Longevity assessments indicated that the 3wt% Sc2O3-doped cathode had been stable for over 4200 hours without significant degradation under an initial load of 0.5 A/cm2 at 1400℃. Finaly, those cathodes had been analyzed by the XRD, SEM, EDS, AES respectively. The analysis results showed that during thermionic emission testing, the Sc2O3 and Y2Hf2O7 had undergone substitutional solid solution reactions, forming the ScxY(2-x)Hf2O[7+(3/2)x] solid solution. This process induced lattice distortion in the Y2Hf2O7, placing it in a high-energy state and thereby reducing the work function on the cathode’s surface. Concurrently, Sc from Sc2O3 displaced Y within the Y2Hf2O7 unit cells, with the displaced Y existing in a metallic form, which enhanced the electrical conductivity of the cathode's surface. Additionally, the ScxY(2-x)Hf2O[7+(3/2)x] solid solution generated a substantial number of Vo2+ oxygen vacancies and free electrons, further augmenting surface conductivity. Collectively, these mechanisms contributed to a marked enhancement in the cathode's thermionic emission capacity.
,
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High-entropy alloy (HEA) microfibers exhibit promising prospects in microscale high-tech applications owing to their exceptional mechanical properties and stability. However, the strength-plasticity tradeoff largely hinders their further industrial applications. Heat treatment can optimize the mechanical properties of HEA microfibers. However, it should be noticed that conventional heat treatment (CHT) faces challenges in precisely regulating microstructures within short durations while being prone to grain coarsening that compromises performance. This study employs an electric current treatment (ECT) technique to finely modulate the properties of cold-drawn CoCrFeNi high-entropy alloy microfibers at the microscale (~70 μm diameter), systematically investigating the effects of thermal and athermal effects during ECT on microstructure and mechanical properties via electron back scatter diffraction, transmission electron microscopy, and synchrotron radiation. A recrystallization, nucleation, and growth model for HEA microfibers is established. Compared to CHT, the synergistic effects of electron wind force and Joule heating during ECT significantly accelerate recrystallization kinetics, yielding finer and more homogeneous grains with a great decrease in dislocation density, and finally lead to better mechanical properties. The ECT-processed HEA microfibers achieve a yield strength ranging from 400 to 2033 MPa and a tensile elongation reaching 53%, which are markedly higher than those of CHT samples. This work demonstrates that ECT is effective for optimizing the microstructure and properties of HEA microfibers. Meanwhile, the results obtained here can provide both a theoretical foundation and technical guidance for the fabrication of high-performance metallic microfibers.
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Hydrogen is widely considered as an ideal alternative energy resource because of its high efficiency, abundance, nonpollution, and renewable nature. One of the main challenges is finding efficient materials that can store hydrogen safely with rapid kinetics, favorable thermodynamics, and high hydrogen density under ambient conditions. The nanomaterial is one of the most promising hydrogen storage materials because of its high surface to volume rate, unique electronic structure and novel chemical and physical properties. In this study, the hydrogen storage properties of Na-decorated Bn(n=3 - 10) clusters are investigated using dispersion-corrected density functional theory and atomic density matrix propagation (ADMP) simulations. The results demonstrate that Na atoms can stably bind to Bn clusters, forming BnNa2 complexes. The average binding energies of Na atoms on the host clusters (1.876-2.967 eV) are significantly higher than the cohesive energy of bulk Na (1.113 eV), effectively preventing aggregation of Na atoms on the cluster surface. Furthermore, when Na atoms bind to Bn (n=3 - 10) clusters, electrons transfer from Na to B atoms, resulting in positively charged Na atoms. Hydrogen molecules are moderately polarized under the electric field and adsorbed around Na atoms through electrostatic interactions. The H-H bonds are slightly stretched but do not break. The Na-decorated Bn clusters can adsorb up to 10 hydrogen molecules with average adsorption energies of 0.063-0.095 eV/H₂ and maximum hydrogen storage densities reaching 11.57-20.45 wt%. Almost no structural change is observed in the host clusters after hydrogen adsorption. Molecular dynamics simulations reveal that the desorption rate of hydrogen molecules increases with temperature. At ambient temperature (300 K), BnNa2 (n=3-8) clusters achieve complete dehydrogenation within 262 fs, while B9Na2 and B10Na2 clusters exhibit a dehydrogenation rate of 90% within 1000 fs. The Na-decorated Bn(n=3-10) clusters not only exhibit excellent properties of hydrogen storage but also enable efficient dehydrogenation at ambient temperature. Thus, BnNa2 (n=3-10) clusters can be regarded as highly promising candidates for hydrogen storage.
, , Received Date: 2025-03-03
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In order to further investigate the non-reciprocity of light propagation in the defective atomic lattices, and due to its effective application in designing novel photonic devices, such as all-optical diodes and isolators, which are powerful tools for information processing and quantum simulation, we innovatively propose to use the Fibonacci sequence to modulate the arrangement of empty lattice cells that form a quasi periodic defective atomic lattices. In the electromagnetically induced transparency window, the probe light is almost not absorbed under the control of a strong coupling field (see Fig. 1 ). The numerical simulation indicates that a wide nonreciprocal reflection band can be achieved by modulating the number of filled lattice cells, Fibonacci sequence, the period number in a single quasi period (see Fig. 2 ). These results provide more degrees of freedom for regulating nonreciprocal reflection with wide bandwidth and high contrast, and have potential applications in quantum computing and information processing.
,
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With the advancements in hardware-optimized deployment of Spiking Neural Networks (SNNs), SNN processors based on Field-Programmable Gate Arrays (FPGAs) have become a research hotspot due to their efficiency and flexibility. However, existing methods rely on multi-timestep training and reconfigurable computing architectures, which increase computational and memory overhead, reducing deployment efficiency. This work presents a high-efficiency, lightweight residual SNN accelerator that couples algorithmic and hardware co-design to optimize inference energy efficiency. On the algorithm side, we employ single-timesteps training, integrate grouped convolutions, and fuse Batch Normalization (BN) layers, compressing the network to only 0.69 M parameters. Quantization-aware training (QAT) further constrains all weights and activations to 8-bit precision. On the hardware side, intra-layer resource reuse maximizes FPGA utilization, a fully pipelined cross-layer architecture boosts throughput, and on-chip Block RAM (BRAM) stores both network parameters and intermediate results to improve memory efficiency. Experimental results demonstrate that the proposed processor achieves an 87.11% classification accuracy on the CIFAR-10 dataset, with an inference time of 3.98 ms per image and an energy efficiency of 183.5 FPS/W. Compared to mainstream Graphics Processing Unit (GPU) platforms, it achieves over twice the energy efficiency. Furthermore, compared to other SNN processors, it achieves at least a 4×improvement in inference speed and a 5×improvement in energy efficiency.
,
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We investigate the properties of the color-flavor-locked (CFL) quark matter at finite temperature and under strong magnetic fields within quasiparticle model. Our results indicate that the pressure of CFL quark matter may become anisotropic under strong magnetic fields, and the equations of state (EOS) and the equivalent quark mass can be strongly influenced by the temperature, the energy gap constat Δ, and the strong magnetic fields inside the CFL quark matter. The equivalent quark mass of CFL quark matter decreases with the increment of the temperature and magnetic field strength, which implies a inverse magnetic catalysis phenomenon. The results also indicate that the entropy per baryon of the CFL quark matter increases with the temperature and decreases with Δ. Furthermore, we study the properties of the CFL magnetars in different isentropic stages, and the results indicate that the star mass and radius is mainly dependent on the strength and orientation distributions of the magnetic field inside the CFL magnetars. The maximum star mass increases with the entropy per baryon, and the temperature of the star matter increases at the large isentropic stages. Moreover, our results also suggest that the polytropic index of the CFL quark matter decrease with the increment of the star mass.
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