Families of slowly changing nonsingular large sparse linear systems arise frequently in many simulation problems in science and engineering. We consider iterative solution with recycling techniques for a general case where both left-hand sides and right-hand sides of the systems change from one family to the next. We firstly develop a generalized product-type method in the framework of recycling biconjugate gradient method (RBiCG), referred to as RGPBiCG, which can also be considered as a recycling variant of GPBiCG. However, as the same situation in RBiCG stabilized method (RBiCGSTAB), the construction of recycling spaces in RGPBiCG requires expensive computational costs due to invoking other algorithms (like RBiCG) to compute approximate eigenspaces. In order to further reduce such computational costs, we alternatively form the recycling spaces in RGPBiCG with difference vectors of approximate solutions, as employed for loose GMRES (LGMRES), resulting in a more promising algorithm termed as LR-GPBiCG. Numerical experiments on both a set of academic problems and engineering simulation problems demonstrate the efficiency of our proposed algorithms.

The inherent properties of electromagnetic metamaterials, such as their large-scale, periodic, multi-media, and complex geometric structures, make the Finite Element Method with the Domain Decomposition Method (FEM–DDM) an ideal simulation approach. Coupling FEM–DDM with the boundary element method (BEM) can further improve solution accuracy. In this work, an efficient non-conformal FEM–BEM–DDM method for electromagnetic scattering analysis of metamaterials is developed. This method employs FEM–DDM for internal finite-periodic metamaterial modeling, coupled with BEM for open-domain electromagnetic analysis. Moreover, a series of computational techniques have been developed for metamaterial electromagnetic analysis. To minimize computational complexity, non-matching mesh and matrix reuse is implemented at the subdomain interfaces, effectively reducing the solution’s degrees of freedom. An efficient three-level preconditioner and the MLFMA are introduced to optimize the efficiency of iterative solution. The proposed method provides an efficient and accurate framework for electromagnetic scattering analysis of metamaterials.

To solve the linear systems with multiple right-hand sides (RHS) arising from the implicit hybridizable discontinuous Galerkin time-domain method for electromagnetic simulations, we propose a block version of the generalized minimal residual method with deflated restarting technique. To accelerate convergence, two improvements are introduced. First, a better strategy is designed to select initial values for restarting a new round of iterations. Second, a multifrontal block incomplete Cholesky factorization is employed as the preconditioner. Numerical results demonstrate its efficiency in computing multiple RHS problems.

While existing models have achieved significant progress on fault diagnosis tasks, what interpretable temporal dependencies they capture to resist noise remains unclear. Previous studies have ignored the inherent non-stationary property of fault data, which is the basis for capturing reliable temporal dependencies under heavy noise operating scenarios. To tackle the aforementioned problems, we propose a non-stationary perception network (NPFormer). Firstly, we revisit the large kernel design in the early stage of the network, and we demonstrate that this can make the attention map more stable for modeling non-stationary series, which can be a more powerful paradigm with heavy noise interference. Secondly, an adaptive non-stationarity embedding block is developed, which breaks the raw data into multiple components and adaptively attenuates the non-stationarity of mechanical signals for better predictability. Finally, we design multi-scale fusion attention to capture fine-grained features with the global scope, while achieving localized spatial-temporal correlations. Extensive experiments have been conducted on three public datasets and the practical aero-engine engineering application, showing that NPFormer significantly outperforms existing state-of-the-art methods. The weight information is visualized to reveal how NPFormer works, which can demonstrate that the stable attention map is a clear clue of anti-noise. We quantitatively reveal the effect of noise on the model, and the model's anti-noise clues, during model inference. Code and models will be available for further study.

In recent years, many engineering applications, such as target detection, stealth, radar, antennas and other fields, are urgently needed to carry out the analysis and research on the electromagnetic scattering and radiation characteristics of complex targets. At present, the method of moments (MoM) based on integral equation is widely used because of its high precision characteristics. However, MoM will produce a dense matrix, which will likely affect the computational performance for large-scale problems. Therefore, many fast algorithms have been derived. In this paper, we focus on the foundational study on matrix generation. We use the vector basis function as the Rao-Wilton-Glisson (RWG) function. By basis function expansion and derivation, we can get a simpler system discrete form, which can be easy to program. Finally, numerical results show that this proposed method is in good agreement with HFSS software, which illustrate that this proposed method is feasible.

A polarization-reconfigurable metasurface wideband antenna with dual polarization and a low radar cross section (RCS) is presented. The antenna employs a diode positioned between two transmission lines to control the current direction and a resistor on a defected-ground branch to manage phase shifts, enabling seamless transitions between circular polarization and linear polarization. The elliptical metasurface design contributes to a reduced RCS. The design results are verified through measurement, showing an impedance bandwidth (IBW) of 49.1%, an axial ratio bandwidth (ARBW) of 23.2% for the diode is off, an IBW of 36.4% for the diode is on, the IBW of the connected resistor is 40.7%, and the peak gains for the three states are 6.4 dBi, 4.4 dBi, and 4.2 dBi, respectively. The metasurface achieves a low RCS bandwidth ranging from 2 GHz to 24 GHz, showing a 6 dBsm reduction in RCS from 4.9 GHz to 19.7 GHz, which corresponds to a 120.3% decrease compared to a perfect electric conductor (PEC) plate.

In this letter, an efficient radiation analysis method for large-scale finite periodic array antenna is proposed. This method is based on finite element domain decomposition and leverages the periodicity of array antenna elements to achieve memory reduction through subdomain matrix reuse. Meanwhile, a matrix preconditioner tailored for finite element domain decomposition is further employed, and an equivalent boundary method is adopted to simplify the computational complexity of multilayer thin-sheet dielectric structures. Subsequently, a far-field equivalence computation method is employed, which directly derives the far-field distribution of large-scale arrays by solving small-scale array problems, thereby significantly lowering the complexity of radiation analysis in large-scale antenna arrays. This method enables computationally efficient radiation analysis of large-scale arrays, even with thousands of elements, significantly reducing processing time and resource demands.

AlGaN-based deep ultra-violet (DUV) LEDs, which emit in the 200-280 nm range, hold great promise for applications in water and air purification, sterilization, and medical diagnostics while light extraction efficiency (LEE) is a primary bottleneck for improving the overall efficiency of deep-ultraviolet light-emitting diodes (DUV LEDs). In this study, guided by finite-difference time-domain (FDTD) simulations, we designed and fabricated Ag-nanodot/Ti/Al reflective p-contacts with an ultra-thin Ti barrier for DUV LEDs. The results demonstrated a 36% increase in wall plug efficiency (WPE) while maintaining good ohmic contact when Ti thickness decreased from 100 to 5 nm. Scanning electron microscope (SEM) analysis revealed the robust stability of the contact structure. The WPE (@51.7 A/cm(2), 40 mA) and LEE of the DUV LEDs with Ag-nanodot/Ti/Al p-contacts of 5-nm-thick Ti reached 4.42% and 9.575%, respectively. The results highlight the importance of p-contact reflectivity in achieving high-efficiency DUV LEDs and demonstrate a feasible route for improving the light output power (LOP) of DUV LEDs. This involves optimizing the reflector through metal-composite engineering, guided by FDTD simulations.

In this article, an ultrawideband (UWB) filtering phased array antenna is proposed based on the tightly coupled dipole concept by introducing short-terminal vias and open terminal vias in the radiation unit cells. The short-terminal vias and the open-terminal vias contribute to the low and high radiation nulls, respectively, which are also evaluated simply. Then, a vertical integrated Marchand balun is applied to feed the coupled dipole and the short-terminal vias are combined as its ground via array. Thus, the proposed UWB filtering phased array antenna can be designed using the multilayer printed circuit broad (PCB) with low profile. To achieve a large ratio between via height and via diameter, the BGA-via technique is also used for the phased array antenna design. Then, the active reflection coefficients are simulated and the resonances within its operating band are analyzed for theta = 60 degrees scan in the E-plane and H-plane. Finally, a phased array antenna prototype is fabricated and assembled to demonstrate the designed performances, including active voltage standing wave ratio (VSWR), antenna gain, and antenna patterns from 5 to 15.5 GHz. About 15-dB radiation suppression performances can be provided out of the band, which can be further improved by cooperating with the front-end chips to relieve the application of the high-performance filter chips in the array. The measured results show agreement with the simulated ones, and the discrepancies at low frequencies are caused by the air gaps within the array.

The domain decomposition method (DDM) enables efficient simulation of electromagnetic problems in large-scale array antennas using full-wave methods on moderate hardware. This paper introduces and compares two nonoverlapping DDMs serving as preconditioners with outstanding simulation efficiency. The first method targets finite periodic array antennas by transforming a single array unit rather than explicitly modeling the entire array, effectively leveraging repetitive structures to significantly reduce memory usage and computation time. The second method applies to universal array antennas with arbitrary geometries, employing both planar and nonplanar mesh-based domain partitioning at subdomain interfaces for flexible modeling of complex arrays. To further enhance computational performance, we propose a parallel multilevel preconditioner based on the block Jacobi preconditioner, thereby accelerating the solution efficiency of subdomain matrix equations in both methods. Additionally, since the choice of domain partitioning method significantly impacts the computational efficiency of DDMs, we propose three different subdomain partitioning strategies. These strategies enable us to accelerate computations while expanding our capacity to simulate a wider variety of types of cases. We developed a fast electromagnetic radiation simulation tool utilizing these techniques. Simulations of exponentially tapered slot (Vivaldi) antenna arrays and antenna arrays with radomes demonstrate that our tool achieves accuracy comparable to commercial software, and notably, our tool outperforms commercial software in terms of the speed of iterative solutions.

Recent advancements in 3D generation models have opened new possibilities for simulating dynamic 3D object movements and customizing behaviors, yet creating this content remains challenging. Current methods often require manual assignment of precise physical properties for simulations or rely on video generation models to predict them, which is computationally intensive. In this paper, we rethink the usage of multi-modal large language model (MLLM) in physics-based simulation, and present Sim Anything, a physics-based approach that endows static 3D objects with interactive dynamics. We begin with detailed scene reconstruction and object-level 3D open-vocabulary segmentation, progressing to multi-view image in-painting. Inspired by human visual reasoning, we propose MLLM-based Physical Property Perception (MLLM-P3) to predict mean physical properties of objects in a zero-shot manner. Based on the mean values and the object's geometry, the Material Property Distribution Prediction model (MPDP) model then estimates the full distribution, reformulating the problem as probability distribution estimation to reduce computational costs. Finally, we simulate objects in an open-world scene with particles sampled via the Physical-Geometric Adaptive Sampling (PGAS) strategy, efficiently capturing complex deformations and significantly reducing computational costs. Extensive experiments and user studies demonstrate our Sim Anything achieves more realistic motion than state-of-the-art methods within 2 minutes on a single GPU.

One of unique features of non-Hermitian systems is the extreme sensitive to their boundary conditions, e.g., the emergence of non-Hermitian skin effect (NHSE) under the open boundary conditions, where most of bulk states become localized at the boundaries. In the presence of impurities, the scale-free localization can appear, which is qualitatively distinct from the NHSE. Here, we experimentally design a disordered non-Hermitian electrical circuits in the presence of a single non-Hermitian impurity and the nonreciprocal hopping. We observe the anomalous scale-free accumulation of eigenstates, opposite to the bulk hopping direction. The experimental results open the door to further explore the anomalous skin effects in non-Hermitian electrical circuits.

In this letter, a wideband circular polarized (CP) antenna based on a double ridge gap waveguide (GWG) with endfire radiation is proposed. The symmetric tapered slots are etched for CP condition. The periodic ridge structures are introduced between the transition ridge and periodic pins to increase the current path. By this means, the appropriate phase differences of orthogonal electric fields are achieved within a compact radiation aperture. The bent dipoles are added at the end of the tapered slot to improve the amplitude and phase condition at lower frequency. Additionally, the gradient transitions from the ridge to the radiation aperture are adjusted for wide impedance matching performance. To validate the proposed antenna, a 1 x 4 CP array fed from the double ridge GWG power divider was fabricated and measured. A measured bandwidth of 32.6% [(28.2 to 39.2) GHz] for both S-11<-10 dB and AR < 3 dB is achieved. Taking advantage of the double ridge GWG, the radiation performances of this antenna are measured with symmetric patterns and a peak gain of 15 dBi. Besides, the efficiency of this antenna is more than 74.5% over the frequency band.

In recent years, emerging self-powered technologies have become a compelling solution in humidity monitoring due to their energy efficiency, environmental friendliness, and suitability for miniaturization. Notably, triboelectric nanogenerators (TENGs) and moisture electric generators (MEGs) exhibit significant advantages because of their high applicability to humidity monitoring. Currently, self-powered humidity sensors have been employed in various areas, including respiratory monitoring, food freshness detection, and environmental humidity measurement. These sensors are capable of detecting humidity across a broad relative humidity (RH) range of 0–100%, with a maximum responsiveness exceeding 100%. Self-powered humidity sensors hold great potential for applications in areas like wearable devices and environmental humidity monitoring. This paper reviews the current state of research on self-powered humidity sensors from four aspects: working mechanisms, performance enhancement, practical applications, and future development. It summarizes the humidity sensing mechanisms of self-powered sensors and elaborates on the recent explorations, major improvements, and directions undertaken by researchers to enhance humidity sensing performance. Finally, it highlights the practical applications of self-powered humidity sensors in various fields and outlines their future development directions. This paper provides a comprehensive summary of the progress made in self-powered humidity sensors and aims to guide future research and development in this field.

The accurate evaluation of aerodynamic characteristics is a prerequisite and foundation for the design of high-performance aerodynamic shapes, navigation guidance, and strength of projectiles. The nonlinearity of aerodynamic calculations for a projectile is high, and the modeling and simulation are difficult, especially under the high-angle of attack flight conditions. Small variations in flight conditions, and structural parameters, etc., may cause large deviations in aerodynamic responses. Taking a small cylindrical projectile as an example, and to realize its attitude control, it is necessary to conduct aerodynamic characteristics analysis on it and analyze the main influencing factors of its aerodynamic characteristics parameters. In this paper, the finite volume method is used to solve the three-dimensional unsteady N-S equation, combined with the SST k-ω turbulence model, the overlapping grid technology, and the forced pitching vibration method, and the aerodynamic characteristics analysis model of the projectile is established, which realizes the accurate simulation of the surrounding flow field, aerodynamic coefficients, and dynamic derivative of the projectile under different flight conditions. On this basis, the Sobol global sensitivity analysis method based on the augmented radial basis function surrogate model of aerodynamics characteristics and Latin hypercube sampling is used to efficiently analyze and obtain the main influence parameters of cylindrical projectile aerodynamic characteristics. This paper provides a basic theory and fast algorithm for subsequent engineering system design, which has important theoretical and engineering value.

In high-latitude areas,the icing period is inevitable during winter.In view of the special mechanical environment of ice cracks faced during underwater launching in low-temperature ice zones,it is of great engineering value to expand the application of submarine-launched marine equipment in a low-temperature ice zone.The presence of floating ice inevitably enhances the nonlinearity of submarine-launched vehicles during high-speed water exit.A 6-degree-of-freedom(DOF)motion model of the vehicle was built by using the dynamic fluid interaction module(DFBI).Through comparative analysis of the underwater and cross-water motion stages of the submarine-launched vehicle under different ice hole sizes and shapes,the influence of ice holes on the evolution of the water-exit cavity was explored.The findings indicate that the ice hole has an obvious binding effect on the cavity during the process of water exit,and the binding effect increases with the decrease in ice hole size.For the same shape of the ice hole,a smaller ice hole size is accompanied by a greater impact on the pitching motion characteristics of the vehicle.For the same ice hole size,the circular ice hole has a greater impact on the pitching motion characteristics of the vehicle than square and triangular ice holes.

We are concerned with the numerical simulation of metasurfaces modeled by generalized sheet transition conditions (GSTCs). A hybridizable discontinuous Galerkin (HDG) method is pro-posed to treat the field discontinuity on the metasurface. We briefly recall the mathematical expressions of the surface susceptibility tensors and present the formulations of the HDG method. The numerical examples by simulating monoanisotropic metasurface show that the proposed HDG method can easily adapt to the discontinuities caused by GSTCs. Additionally, we present COMSOL simulation results for the same metasurface to further validate the efficacy of the proposed method.

A 3D finite element terminal simulator based on transfinite element truncation is developed in this paper. According to the multi-conductor transmission line theory and the developed automatic generation algorithm of terminal integral path, the terminal-based parameters can be calculated by this simulator quickly and accurately. The Viawizard through-hole structure is used to verify this simulator.

Aiming at the challenge that existing research on open-set specific emitter identification (SEI) has low identification performance due to high similarity between known classes and unknown classes, this paper proposes an approach based on activation reshaping and important neurons. This method utilizes convolutional neural network (CNN) to extract latent features from the signals of emitter individuals. Specifically, activation reshaping and pruning based on Shapley value are applied in the penultimate layer of the CNN to enhance differentiation between known and unknown emitter individuals. The open-set score derived from model logits and the Energy score function is leveraged in proposed method to effectively discriminate unknown emitter individuals from known emitter individuals, thereby transforming open-set recognition into closed-set recognition. A balanced trade-off between accuracy for known and unknown classes is achieved by the proposed method. Experimental results demonstrate that under various degrees of openness, the proposed method achieves more accurate open-set SEI classification results.

Since H2S gas is flammable and explosive, it has significance to realize H2S detection at room temperature. In this work, different amounts of SnO2 quantum dots (QDs) were loaded on Prussian blue derived α-Fe2O3 hollow cubes, which exhibits an uneven porous granular surface structure evidenced by characterization of TEM and SEM. Aiming H2S as target gas, the α-Fe2O3/SnO2 composites demonstrate greatly improved gas sensing performance at room temperature. Specifically, the response value of S1 to S4 (different SnO2 QDs loads) to 5 ppm H2S at room temperature are 4.97, 5.76, 8.21 and 6.69 respectively, which has a trend from rise to decline as the SnO2 QDs increases. Optimum sensitivity is achieved by 10 wt% SnO2 loading. Finally, characterizations such as BET, XPS and DRIFTS et al. reveal that the effective electron transfer from SnO2 to α-Fe2O3 via energy band match promotes the chemisorption oxygen and density and mobility of charge carriers, which is beneficial to H2S gas sensing.