In recent years, the growing demand for functional textiles has propelled significant advancements in hydrophobic finishing technologies. Despite the exceptional performance of fluorinated hydrophobic materials, increasingly stringent environmental regulations targeting per- and polyfluoroalkyl substances (PFAS) have elevated fluorine-free alternatives to the forefront of research. This paper first systematically reviews the latest progress in typical fluorine-free hydrophobic materials, encompassing paraffin-based, acrylic-based, silicone-based, polyurethane-based, nano-silica modified materials, and bio-based materials, while analyzing their respective performance characteristics. Subsequently, the primary fabrication strategies for fluorine-free hydrophobic surfaces are elaborated, including impregnation, spraying, layer-by-layer self-assembly, electrospinning, sol-gel methods, plasma technology and vapor deposition. Building upon this foundation, the paper focuses on a comprehensive review of application studies involving the integration of multiple functionalities—such as self-cleaning, anti-icing, oil-water separation, and atmospheric water collection—on hydrophobic textile surfaces. Finally, the key challenges currently faced by fluorine-free hydrophobic materials are analyzed, and it is proposed that future research should prioritize the synergistic innovation of molecular design and finishing technologies to develop high-performance, multi-functional, sustainable, and cost-effective fluorine-free hydrophobic surfaces.

Condensed matter systems with coexisting Dirac cones and flat bands and a switchable control between them within a single system are desirable but remarkably uncommon. Here, we report a layered quantum material system, KxNi4S2 (0 <= x <= 1), that simultaneously hosts both characteristics without involving typical Kagome/honeycomb lattices. Enabled by a topochemical K-deintercalation process, the Fermi surface can be fine-tuned continuously over a wide range of energies. Consequently, a non-magnetic Dirac-metal state with a topological nontrivial Z 2 index of 1;(000), supported by first-principles calculations and high mobility up to 1,471 cm2V-1 s-1 , is observed on the K-rich x = 1 side, whereas a flat-band-induced antiferromagnetic state with TN up to 10.1 K emerges as the K-content approaches 0. The KxNi4S2 system offers a versatile platform for exploring emerging phenomena and underscores aviable pathway for in situ control of quantum materials dominated by Dirac cones, flat bands, and their interplay.

In this paper, we present a comprehensive study of magnetic properties of Co3Sn2S2 (CoSnS) crystals using macroscopic characterization and observations of the domain structure (DS) in a wide range of easy- and hard-axis fields (H) and temperatures (T). From macroscopic measurements, we derive temperature dependences of the basic magnetic parameters of the material [saturation magnetization Ms(T), uniaxial anisotropy constant K(T), and exchange stiffness A(T)] and, based on them, calculate the thermodynamic magnetization M(H,T) curves and DS parameters for pinning-free samples. We find important qualitative and quantitative differences between the theory and experiment defined by the efficient pinning of domain walls (DWs) in our samples. It turns out that, already at temperatures close to the ferromagnetic transition Tc, the DW dynamics falls into the heavy creep regime, resulting in a strong deferral of the DS adjustment into the equilibrium state. We suggest that specific magnetic defects, responsible for pinning and causing field-tuned reproducible domain nucleation patterns observed in our high-quality samples, are pointlike. Recently found magnetic polarons formed around vacancies and impurities, which carry strong diamagnetic moments of spin-orbit nature and are intrinsic for CoSnS and expected in other Weyl semimetals, are a possible source of pinning yielding peculiar M(H,T) response of CoSnS.

Emerging from the intricate interplay of topology and magnetism, the giant anomalous Hall effect (AHE) is the most known topological property of the recently discovered kagomé ferromagnetic Weyl semimetal Co3Sn2S2 with the magnetic Co atoms arranged on a kagomé lattice. Here it is reported that the AHE in Co3Sn2S2 can be fine-tuned by an applied magnetic field orientated within ≈2° of the kagomé plane, while beyond this regime, it stays unchanged. Particularly, it can vanish in magnetic fields parallel to the kagomé plane and even decrease in magnetic fields collinear with the spin direction. This tunable AHE can be attributed to local spin switching enabled by the geometrical frustration of the magnetic kagomé lattice, revealing that spins in a kagomé ferromagnet change their switching behavior as the magnetic field approaches the kagomé plane. These results also suggest a versatile way to tune the properties of a kagomé magnet.

Frequency diverse array (FDA) exhibits a phenomenon of distance-angle coupling, and existing decoupling methods suffer from drawbacks, such as high sidelobe levels and computational inefficiency. However, traditional joint optimization methods face challenges of computational inefficiency and convergence issues by jointly optimizing frequency deviation and element positions. This letter proposes a FDA decoupling method based on sequential convex optimization technology, which employs Taylor expansion techniques to approximate this high-dimensional nonconvex optimization problem as a series of convex optimization subproblems, enabling efficient solution. Simulation results demonstrate that the proposed method not only further improves the performance of the FDA antenna but also exhibits higher computational efficiency compared to heuristic optimization algorithms.

Impulse radio ultrawideband (IR-UWB) radar has the advantages of low cost, high resolution, and independence of light and weather conditions. Its potential in human activity recognition (HAR) for IoT device sensing draws interest. One challenge in this domain is effectively representing spatial static and temporal dynamic information in echo sequences. Transformers, used extensively in NLP and CV, have powerful sequence long-range dependency modeling capabilities. However, in the field of radar HAR, the application research of transformers is still insufficient. In addition, there is currently a lack of publicly available IR-UWB radar human action data sets. To this end, we proposed various fine-grained feature image calculation methods and designed an IR-UWB Radar Human Activity data set (IURHA2023). This article presents a swin transformer encoder combining cosine similarity attention and patch overlap to obtain deep spatio-temporal features of human action feature images. Compared with other proposed transformer models or traditional CNNs and RNNs, the improved swin transformer encoder performs better. To further improve the feature learning capability of the backbone network and the robustness to echo variations, we propose a supervised contrastive learning-enhanced swin transformer (SCL-SwinT). It obtains distinctions and compact embeddings by comparing the similarities of positive and negative examples partitioned according to labels. Experimental results on the IURHA2023 data set show that SCL-SwinT achieves a recognition rate exceeding 90%, and the inference speed on IoT edge devices satisfies real-time applications. Ablation experiments demonstrate the effectiveness of the proposed components. In addition, SCL-SwinT exhibits good robustness to environmental factors like noise, multipath, and distance.

This paper investigates null control within the transmit–receive beampattern of Frequency Diverse Array-Multiple-Input and Multiple-Output (FDA-MIMO) systems, presenting a novel phase-only optimization approach for achieving null control in FDA-MIMO. We employ an alternating multiplier framework, which transforms the intricate and inherent constant modulus constraint and numerous amplitude constraints in optimization into more manageable projection problems. By employing a phase-only optimization strategy, the intricate hardware and computational burdens associated with null control in FDA-MIMO are effectively alleviated. The simulation results indicate that the algorithm proposed in this paper exhibits excellent null control ability while precisely maintaining constant modulus constraints, and it possesses an extremely high computational efficiency.

AbstractThis letter presents a model based on the Cramér–Rao bound theory for calculating the theoretical lower limit of imaging resolution of microwave computational imaging aided by re‐configurable metasurface. The model takes into account two crucial parameters: the signal‐to‐noise ratio and the number of measurements in the imaging process. By simultaneously considering the signal‐to‐noise ratio and the number of measurements, as well as other parameters, the model allows for a comprehensive assessment of the imaging resolution of the imaging system. In addition, both position estimation and intensity estimation are considered, and a new composite statistical resolution concept is proposed, which is more suitable for microwave computational imaging.

TaCo2Te2 is recently reported to be an air-stable, high mobility van der Waals material with probable magnetic order. Here we investigate the scaling behavior of its magnetoresistance. We measured both the longitudinal (pxx) and Hall (pxy) magnetoresistivities of TaCo2Te2 crystals in magnetic fields parallel to the c axis and found that the magnetoresistance violates the Kohler's rule MR similar to f [H/p0] while obeying the extended Kohler's rule MR similar to f [H/(nT p0)], where MR similar to [pxx(H) - p0]/p0, H is the magnetic field, nT is a thermal factor, and pxx(H) and p0 are the resistivities at H and zero field, respectively. While deviating from those of the densities of electrons (ne) and holes (nh) obtained from the two-band model analysis of the magnetoconductivities, the temperature dependence of nT is close to that of the Hall carrier densities nH calculated from the slopes of pxy(H) curves at low magnetic fields, providing a different way to obtain the thermal factor in the extended Kohler's rule.

Abstract The range‐angle coupling characteristics of traditional frequency diverse array (FDA) will deteriorate target localization performance. To address this problem, several decoupling methods for FDA have been developed in the past decade, mainly including deterministic methods and global optimization methods. However, most of these methods are based on frequency offset design and do not fully utilize other design degrees of freedom, such as excitation and element spacing, which limits obtained pattern performance. In this letter, a low‐sidelobe FDA pattern synthesis method is proposed by jointly optimizing frequency offset, array spacing and excitation. The entire optimization process is treated as two sub‐optimization problems, that is, a non‐convex sub‐problem involves frequency offset and array spacing, and a convex sub‐problem involves excitation. By integrating the mayfly algorithm and convex programming techniques, this synthesis problem can be effectively solved. Compared with the current state‐of‐the‐art counterparts, the proposed method takes full advantage of the FDA's design freedom and generates a doted beampattern with lower sidelobes.

Microwave computational imaging (MCI) employs uncorrelated illumination patterns via meta-materials to multiplex the information content of an entire scene into a few simple measurements, enabling image reconstruction through computational strategies. However, the reconstruction process often involves solving an ill-conditioned equation iteratively, which can result in a high computational burden and challenges in ensuring real-time performance. This paper presents a wavenumber spectrum reconstruction (WSR) method for fast imaging with reprogrammable metasurface (RMS). By constructing a series of code configurations, the electric field spectrum at the position of the RMS is measured. Then the wavenumber spectrum of the target is calculated by compensation in the wavenumber domain. Finally, the reconstruction of the target image is performed by inverse Fourier transformation (IFT) operation, which is less computationally burdensome and less time consuming. The proposed approach enables the construction of code configurations independent of the target's location and shape, thereby reducing the difficulty of optimizing measurement patterns. Simulation results show that the WSR method outperforms the traditional compressed sensing method in reconstructing target images with a low signal-to-noise ratio while significantly reducing computation time. The proposed method can satisfy the requirements for real-time performance and noise immunity in MCI systems, and can also be implemented on hardware platforms with limited computing resources.

A low-profile broadband circularly polarized (CP) patch antenna with wide axial-ratio beamwidth (ARBW) is presented in this letter. The proposed antenna adopts two substrates, one of which is printed with a feeding network composed of the Wilkinson power dividers cascaded with the Schiffman phase shifters to contribute to the broadband CP property. A circular patch with four L-shaped branches as a radiator printed on another substrate is employed to obtain wide ARBWs. A wideband CP radiation is achieved by utilizing TM 11 , TM 11+, and TM 31 mode. An antenna prototype with dimensions of 1.03 λ 0 × 1.03 λ 0 × 0.025 λ 0 (λ 0 is the wavelength at the center frequency) is fabricated. The measurement results reveal that a wide relative impedance bandwidth of about 55.6% can be achieved in the 3.26–6.04 GHz, and the CP bandwidth is 33.0% (3.85–5.50 GHz). At 5.0 GHz, the 3 dB ARBWs of the xoz plane and the yoz plane are 148° and 220°, respectively.

We introduce a design modification to conventional geometry of the cryogenic three-terminal switch, the nanocryotron (nTron). The conventional geometry of nTrons is modified by including parallel current-carrying channels, an approach aimed at enhancing the device's performance in magnetic field environments. The common challenge in nTron technology is to maintain efficient operation under varying magnetic field conditions. Here, we show that the adaptation of parallel channel configurations leads to an enhanced gate signal sensitivity, an increase in operational gain, and a reduction in the impact of superconducting vortices on nTron operation within magnetic fields up to 1 T. Contrary to traditional designs that are constrained by their effective channel width, the parallel nanowire channels permits larger nTron cross sections, further bolstering the device's magnetic field resilience while improving electro-thermal recovery times due to reduced local inductance. This advancement in nTron design not only augments its functionality in magnetic fields but also broadens its applicability in technological environments, offering a simple design alternative to existing nTron devices.

Recently, anomalies in the temperature dependences of the carrier density and/or mobility derived from analysis of the magnetoresistivities using the conventional two-band model have been used to unveil intriguing temperature-induced Lifshitz transitions in various materials. For instance, two temperature-driven Lifshitz transitions were inferred to exist in the Dirac nodal-line semimetal ZrSiSe, based on two-band model analysis of the Hall magnetoconductivities where the second band exhibits a change in the carrier type from holes to electrons when the temperature decreases below T = 106 K and a dip is observed in the mobility versus temperature curve at T = 80 K. Here, we revisit the experiments and two-band model analysis on ZrSiSe. We show that the anomalies in the second band may be spurious, because the first band dominates the Hall magnetoconductivities at T > 80 K, making the carrier type and mobility obtained for the second band from the two-band model analysis unreliable. That is, care must be taken in interpreting these anomalies as evidences for temperature-driven Lifshitz transitions. Our skepticism on the existence of such phase transitions in ZrSiSe is further supported by the validation of the Kohler's rule for magnetoresistances at temperatures below 180 K. This work showcases potential issues in interpreting anomalies in the temperature dependence of the carrier density and mobility derived from the analysis of magnetoconductivities or magnetoresistivities using the conventional two-band model.

Titanium nitride is a material of interest for many superconducting devices such as nanowire microwave resonators and photon detectors. Thus, controlling the growth of TiN thin films with desirable properties is of high importance. This work aims to explore effects in ion beam-assisted sputtering (IBAS), were an observed increase in nominal critical temperature and upper critical fields are in tandem with previous work on Niobium nitride (NbN). We grow thin films of titanium nitride by both, the conventional method of DC reactive magnetron sputtering and the IBAS method, to compare their superconducting critical temperatures [Formula: see text] as functions of thickness, sheet resistance, and nitrogen flow rate. We perform electrical and structural characterizations by electric transport and x-ray diffraction measurements. Compared to the conventional method of reactive sputtering, the IBAS technique has demonstrated a 10% increase in nominal critical temperature without noticeable variation in the lattice structure. Additionally, we explore the behavior of superconducting [Formula: see text] in ultra-thin films. Trends in films grown at high nitrogen concentrations follow predictions of mean-field theory in disordered films and show suppression of superconducting [Formula: see text] due to geometric effects, while nitride films grown at low nitrogen concentrations strongly deviate from the theoretical models.

Abstract Due to the controllable degrees of freedom of frequency diverse array in the distance dimension, the frequency diverse multiple‐input multiple‐output (FDA‐MIMO) radar can easily deal with mainlobe interference, which is often difficult to solve in traditional phased arrays. Nevertheless, the performance of FDA‐MIMO radar will suffer from degradation in the scenario where spectrum interferences and signal‐dependent interferences coexist. In order to solve this problem, a novel FDA‐MIMO radar framework via antenna switching is proposed. Based on this framework, an effective method for jointly optimising antenna selection and beamforming against spectrum interferences and signal‐dependent interferences is developed. The resulting optimization problem is nonconvex and NP‐hard owing to the integer constraints caused by antenna selection. By relaxing the integer constraints, the original problem can be transformed into a convex optimization form and an iterative reweighting strategy is used to force the obtained solution to satisfy the integer constraints. Simulation examples show that the proposed algorithm has better performance in output signal‐to‐interference‐plus‐noise ratio (SINR) and beampattern radiation performance than the existing competitive methods.

The problem of distributed collaborative guidance under the time delay caused by multiple missiles is investigated in this paper, and a distributed collaborative guidance law is proposed. Using graph theory, we analyzed the local communication topology among missiles and established a leader–follower collaborative communication model and closed–loop guidance system. Furthermore, by introducing a neutral operator in the guidance law and based on the Lyapunov theory, we investigated the asymptotic stability of the cooperative guidance model with constant time delay. We demonstrated that the guidance error converges to a bounded value. Finally, this guidance method’s effectiveness was validated through numerical simulations.

Magnetism plays a key role in the emergence of topological phenomena in the Weyl semimetal Co3Sn2S2, which exhibits a ferromagnetic (FM) interactions along the c-axis of the crystal and an antiferromagnetic (AFM) interactions within the ab plane. Extensive studies on the temperature dependence of the magnetism with the magnetic field along the c-axis have uncovered a number of magnetic phases. Currently, the nature and origins of the reported magnetic phases are under debate. Here we report on magnetic field orientation effects on the magnetism in Co3Sn2S2. The shape of the hysteresis loop of the Hall resistance at a fixed temperature is found to change from rectangular to bow-tie-like as the magnetic field is tilted from the c-axis towards the ab plane, resembling that reported for magnetic fields along the c-axis as the temperature approaches the Curie temperature from below. Unlike their temperature-dependent counterparts, the newly observed bow-tie-like hysteresis loops show exchange bias. Our results showcase the contribution of the in-plane AFM interactions to the magnetism in Co3Sn2S2 and demonstrate a new way to tune its magnetic phases. They also shed light on the temperature-dependent magnetic phases occurring in the magnetic field along the c-axis of the crystal.

An innovative architecture, termed Spike-Timing-Dependent Plasticity Convolutional Spiking Neural Network (STDP-CSNN), is proposed for efficient radar-based gesture recognition in this paper. Radar range-Doppler image data are encoded into spike sequences with CSNN, and the leaky integrate-and-fire (LIF) model is employed as a neuron in the network nodes. This design enables efficient accumulation and transmission of spike signals, resulting in a significant reduction in network power consumption. Furthermore, the unsupervised learning algorithm of STDP is employed to facilitate feature extraction in the established CSNN, ensuring low computational complexity. The experimental results demonstrate that the proposed STDP-CSNN architecture achieves an impressive recognition accuracy of 92.72%, while concurrently addressing the crucial requirements of low power consumption and computational simplicity.

By controlling the null distribution in the range-angle dimension, the frequency diverse array (FDA) can handle range-dependent interference, which is usually difficult to solve for the traditional phased array. However, the current investigations focus more on the design of weights for null control, ignoring the unique design dimension of FDA, that is, the frequency offsets. Therefore, the array potential cannot be fully exploited to maximise the range-dependent interference suppression capability. In this paper, a novel FDA synthesis method with large null depth is proposed. By incorporating the mayfly algorithm and convex programing, frequency offsets and transmit weights are jointly optimised to generate maximum null depths in a given region while maintaining the specified array response of the desired target. Other null control methods for FDA are listed as comparison, including weights-only optimisation method, frequency offsets-only optimisation and frequency offsets and weights sequentially optimisation method. Numerical examples demonstrate the superiority of the proposed algorithm.