Hasil untuk "Electricity and magnetism"

Ziqiang PENG, Han WANG, Ruikai XUE et al.

In recent years, surface ship target tracking has been an important issue that needs to be solved in autonomous ship navigation. For three-dimensional environmental perception, LiDAR has the characteristics of high resolution and high precision, for three-dimensional environmental perception. By adding one-dimensional scanning, long-line array LiDAR has a larger field of view compared with single point and area array LiDAR, offering unique advantages in environmental perception. Owing to the inconsistency between the characteristics of surface ships and ground target, and the lack of relevant data sets, the current commonly used fitting methods cannot effectively perceive surface target characteristics. In this paper, an efficient target tracking method for ships is proposed based on the characteristics of single-photon point clouds and long-distance target detection. This method is based on the synchronous clustering and denoising of neighboring points; it uses the prior knowledge of the geometric features of ships to fit through the extraction of ship feature points and surfaces, further reducing the influence of noise. Combined with the extended Kalman filter and velocity estimation method, the real-time and stable trajectory tracking of a 600 m target is realized. The root mean square error of tracking is 0.5 m, with a single-frame processing time of 1.02 s, which meets real-time engineering requirements. The proposed method has also been tested in a complex environment and has a good tracking effect for large ships, which is better than the common fitting tracking method. This provides better information for the subsequent autonomous navigation of intelligent ships, and realizes better obstacle avoidance and path planning for ships.

GAO Zhaoyao, ZHANG Zhan, HU Liangliang et al.

Parallel magnetic resonance imaging (PMRI) is an imaging technique that uses multiple receiver coils for undersampling. It utilizes spatial information to supplement the insufficient gradient phase encoding and reconstructs aliasing-free images with specific algorithms to accelerate the imaging process. To address the issue of overfitting or poor generalization when using high acceleration factors with a limited number of auto calibration signals (ACS) in PMRI algorithms based on specific scans, a reconstruction method based on virtual coils and GRAPPA-enhanced networks is proposed. This method expands the sample by using virtual conjugate coils and enhances the ACS using the GRAPPA algorithm for training a nonlinear deep learning network. Experimental results show that the proposed PMRI method can effectively reduce aliasing artifacts caused by insufficient reference data, significantly improving image reconstruction quality with fewer ACS and higher acceleration factors.

Yan Wang, Suwan Li, Yihan Tong et al.

Rare earth-doped ferroelectric (FE) ceramics have attracted much attention due to their great potential application for novel multifunctional optical-electro devices. This study successfully devised and fabricated tungsten bronze Sr[Formula: see text]SmxAg[Formula: see text] Na[Formula: see text]Nb[Formula: see text]ZrxO[Formula: see text] ceramics, demonstrating exceptional energy storage and luminescent properties suitable for multifunctional capacitors. Effects of co-doping Sm[Formula: see text] and Zr[Formula: see text] in A and B sites on the phases structure, FE, energy storage and photoluminescence properties of Sr[Formula: see text]SmxAg[Formula: see text]Na[Formula: see text]Nb[Formula: see text]ZrxO[Formula: see text] ceramics were systematically investigated. Through employing various collaborative optimization strategies, encompassing the refinement of ceramic grains, the induction of nanodomain generation and the incorporation of large bandgap components, enhancement of breakdown strength and regulation of constructing relaxor FEs were achieved. Encouragingly, the high-performance multifunctional materials with remarkable recoverable energy storage metrics ([Formula: see text] 3.72[Formula: see text]J/cm3, [Formula: see text] 82.7%), brilliant red-orange light emission and distinguished frequency and temperature stabilities within specific ranges were obtained in Sr[Formula: see text]Sm[Formula: see text]Ag[Formula: see text]Na[Formula: see text]Nb[Formula: see text]Zr[Formula: see text]O[Formula: see text] ceramics. Besides, the multifunctional ceramics demonstrated a high-power density (68.1[Formula: see text]MW/cm[Formula: see text], a substantial current density (908.1[Formula: see text]A/cm[Formula: see text] and a fast discharge time (51[Formula: see text]ns) at 190[Formula: see text]kV/cm. These findings suggest that the designed Sr[Formula: see text]SmxAg[Formula: see text]Na[Formula: see text]Nb[Formula: see text]ZrxO[Formula: see text] ceramics hold promise as candidate materials for dielectric capacitors.

T. A. Elwi, A. A. M. Al-Shaikhli, H. H. Al-Khaylani et al.

In this paper, a design of a microstrip antenna based on metamaterial (MTM) and electromagnetic band gap (EBG) arrays. The patch is structured from 5×3 MTM array to enhance the antenna bandwidth gain product. The individual unit cell is structured as a split ring (SRR) with a T-resonator. The ground plane is defected with an EBG to suppress the surface waves diffraction from the substrate edges. The antenna is printed on a Roger substrate with permittivity of 10.2 and 1 mm thickness. It is found that the proposed antenna provides a frequency resonance around 2.45 GHz and 3.5 GHz with another band between 4.6 GHz to 5.6 GHz which are very suitable for Wi-Fi and 5G networks. Nevertheless, the antenna gain is found to vary from 3.5 dBi to less than 6 dBi. The antenna size is reduced enough to λ/5 of the guided wavelength to fit an area of 12 mm×20 mm. The proposed antenna performance is controlled with two PIN diodes for reconfiguration process. The antenna frequency resonance bands are found to be well controlled by stopping the current motion at the particular band. The antenna is fabricated and tested experimentally. Finally, the simulated results are compared to those obtained from measurements to provide an excellent agreement to each other with error of less than 3%.

Xin WU, Chao HU, Qi WANG et al.

When the solid oxide fuel cell (SOFC) operates for a long time at high temperature, due to the repeated start-stop cycle and long-term operation, the reactor is prone to seal failure, which will lead to leakage failure, and then lead to thermal runaway and damage of the reactor, which seriously affects the stability of the system operation. The change of parameters may lead to the occurrence of leakage faults and consequently thermal runaway of the stack or even abnormal system shutdown. Aiming at this fault, a diagnostic method based on the variational mode decomposition (VMD) and Hilbert transform (HT) is proposed through the experiment temperature and voltage signals. This method was applied to experimentally investigate the sealing failure leakage fault in SOFC stacks. The research results demonstrate that utilizing the fault diagnosis method based on VMD and HT can determine the presence of leakage in the stack under open-circuit conditions. By collecting the temperature and voltage signals of the stack and applying this fault diagnosis method, the temperature signal can more rapidly indicate the presence of a leakage fault in the stack. When comparing the diagnosis methods based on Ensemble Empirical Mode Decomposition and VMD, it was found that the latter can detect the leakage fault in the stack 100 seconds faster.

Mohammad Mahdi Taskhiri

Abstract This article uses the ray inserting method to design a low‐cost inhomogeneous lens in the Ku‐band. The focal length to the diametre ratio of the designed lens is 0.45, which is lower than most designed lenses in this area. Also, no approximation is considered to yield the refractive index profile. The refractive index changes from the centre to the sides have been made in two sections to limit the maximum calculated refractive index of the structure to the Plexiglass refractive index. The designed lens proposed a good match to the source and surroundings. The theoretical design is validated by the finite difference time domain scheme and full‐wave simulation. The lens structure is realised and fabricated on a multilayer Plexiglass sheet. The results of simulations and experiments indicate good performances of the designed lens in the wide frequency bandwidth.

Tongliang Yang, Yun Fang, Chengming Zhang et al.

Abstract In order to accurately predict the content and variation trend of dissolved gas in transformer oil and guide the condition maintenance of power transformers, a combined prediction model based on multi‐information fusion is proposed and its effectiveness is analysed. First of all, based on the possibility of pathological and missing historical sample data, a detection and filling method based on variable weight combination samples is established. Second, the authors propose two models. Aiming at the non‐linear and non‐stationary characteristics of gas content, a univariate decomposition prediction mode HBA‐VMD‐TCN which based on the Honey Badger algorithm, variational mode decomposition and time convolutional network (TCN) is established. Then the multivariate Informer prediction model is established for gas content affected by multiple variables. Third, the cross‐entropy theory is used to determine the weight coefficients of the two models, and the multi‐information fusion combined prediction model is formed. Finally, on the basis of the above, a method to determine the time step and the position information of the transition point adaptively in the process of prediction is proposed to further improve the prediction accuracy. The results show that, through a series of simulation experiments of model comparison and transformer anomaly prediction, the accuracy and effectiveness of the combined prediction model are verified.

Trang ThanhTrung, Pham ThanhLong, Hu Yueming et al.

A field is described as a region under the influence of some physical force, such as electricity, magnetism, or heat. It is a continuous distribution in the space of continuous quantities. The characteristics of the field are that the values vary continuously between neighboring points. However, because of the continuous nature of the field, it is possible to approximate a physical field of interpolation operations to reduce the cost of sampling and simplify the calculation. This article introduces the modeling of the parametric intensity of physical fields in a general form based on the interpolation shape function technique. Besides the node points with sample data, there are interpolation points, whose accuracy depends significantly on the type of interpolation function and the number of node points sampled. Therefore, a comparative analysis of theoretical shape functions (TSFs) and experimental shape functions (ESFs) is carried out to choose a more suitable type of shape function when interpolating. Specifically, the temperature field is the quantity selected to apply, analyze, and conduct experiments. Theoretical computations, experiments, and comparisons of results have been obtained for each type of shape function in the same physical model under the same experimental conditions. The results show that ESF has an accuracy (error of 0.66%) much better than TSF (error of 10.34%). Moreover, the field model surveyed by a generalized reduced gradient algorithm allows for identifying points with the required parameter values presented in detail. The illustrated calculations on temperature field control in the article show that the solution for both forward and reverse problems can be determined very quickly with high accuracy and stability. Therefore, this technique is expected to be entirely feasible when applied to thermal control processes such as drying in paint technology, kilns, and heat dissipation in practice.

Werner Ebeling, Gerd Röpke

We study the effective interactions and the mass action constants for pair and triple associations in classical and quantum plasmas. Avoiding double counting, we derive new expressions for the mass action constants. The calculations resulted in values that were substantially smaller than the standard ones in relevant temperature ranges by up to 50 percent. On this basis, we determine the pressure of H, He and Li plasmas and the osmotic coefficient of electrolytes with higher charges such as, e.g., seawater. Classical and quantum Coulomb systems show strong similarities. The contributions in low orders with respect to the interaction <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msup><mi>e</mi><mn>2</mn></msup></semantics></math></inline-formula> are suppressed by thermal and screening effects. The contributions of weakly bound states, near the continuum edge, to the mass action constants are reduced, replacing the exponential functions with cropped exponentials. The new mass action constants are consistent with well-known extended limiting cases of screening effects. We analyze classical examples including the salts CaCl<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>2</mn></msub></semantics></math></inline-formula> and LaCl<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mrow></mrow><mn>3</mn></msub></semantics></math></inline-formula>, and a model of seawater including multiple associations. In the case of quantum systems, we follow the work of Planck–Brillouin–Larkin for H plasmas and study He and Li plasmas. The equation of state (EoS) for wide-density regions is obtained through the concatenation of the EoS for the low-density region of partial ionization with the EoS of degenerate plasmas, where all bound states are dissolved and Fermi, Hartree–Fock and Wigner contributions dominate.

Yunyun Feng, Changhong Yang, Xiaoying Guo et al.

BiScO3–PbTiO3 binary ceramics own both high Curie temperature and prominent piezoelectric properties, while the high dielectric loss needs to be reduced substantially for practical application especially at high temperatures. In this work, a ternary perovskite system of (1–[Formula: see text]–[Formula: see text])BiScO3–[Formula: see text]PbTiO3–[Formula: see text]Bi([Formula: see text][Formula: see text])O3 (BS–[Formula: see text]PT–[Formula: see text]BMS) with [Formula: see text] = 0.005, [Formula: see text] = 0.630–0.645 and [Formula: see text] = 0.015, [Formula: see text] = 0.625–0.640 was prepared by the traditional solid-state reaction method. The phase structure, microstructure, dielectric/piezoelectric/ferroelectric properties were studied. Among BS–[Formula: see text]PT–[Formula: see text]BMS ceramic series, the BS–0.630PT–0.015BMS at morphotropic phase boundary possesses the reduced dielectric loss factor (tan[Formula: see text] = 1.20%) and increased mechanical quality factor ([Formula: see text][Formula: see text] = 84), and maintains a high Curie temperature ( [Formula: see text] = 410[Formula: see text]C) and excellent piezoelectric properties ([Formula: see text][Formula: see text] = 330 pC/N) simultaneously. Of particular importance, at elevated temperature of 200[Formula: see text]C, the value of tan[Formula: see text] is only increased to 1.59%. All these properties indicate that the BS–0.630PT–0.015BMS ceramic has great potential for application in high-temperature piezoelectric devices.

Tao ZHENG, Zemei DAI, Jiahao YAO et al.

Integrated energy system (IES) provides users with diversified energy supply services through the coupling conversion of multiple energy flows. Compared with conventional independent energy supply systems, the IES has greater degree of control freedom. In order to measure the degree of control freedom, this paper firstly proposes a convertibility index to characterize the mutual conversion ability of multiple energy flows, and a substitutability index to represents selection opportunities for alternative energy at the user side. In addition, the calculation methods for the convertibility index and the substitutability index are provided. Secondly, considering the influence of control freedom on the optimal operation of the IES, an economic dispatch model of the cooling-heating-power-gas IES is established. Finally, a case simulation is carried out, and the results shows that improving the two control freedom indexes of the convertibility and substitutability of the integrated energy system can reduce the economic dispatch cost of the system.

Xiangwei DANG, Fei QIN, Xiangxi BU et al.

Multi-sensor fusion perception is one of the key technologies to realize intelligent automobile driving, and it has become a hot issue in the field of intelligent driving. However, because of the limited resolution of millimeter-wave radars, the interference of noise, clutter, and multipath, and the influence of weather on LiDAR, the existing fusion algorithm cannot easily achieve accurate fusion of the data of two sensors and obtain robust results. To address the problem of accurate and robust perception in intelligent driving, this study proposes a robust perception algorithm that combines millimeter-wave radar and LiDAR. Using a new method of spatial correction based on feature-based two-step registration, the precise spatial synchronization of the 3D LiDAR and 2D radar point clouds is realized. The improved millimeter-wave radar filtering algorithm is used to reduce the influence of noise and multipath on the radar point cloud. Then, according to the novel fusion method proposed in this study, the data of the two sensors are fused to obtain accurate and robust sensing results, which solves the problem of the influence of smoke on LiDAR performance. Finally, we conducted multiple sets of experiments in a real environment to verify the effectiveness and robustness of our method. Even in extreme environments such as smoke, we can still achieve accurate positioning and robust mapping. The environment map established by the fusion method proposed in this study is more accurate than that established by a single sensor. Moreover, the location error obtained can be reduced by at least 50%.

Qinchao Zheng, Chenxue Xu, Zhenlin Jiang et al.

Smart actuators refer to integrated devices that are composed of smart and artificial materials, and can provide actuation and dampening capabilities in response to single/multi external stimuli (such as light, heat, magnetism, electricity, humidity, and chemical reactions). Due to their capability of dynamically sensing and interaction with complex surroundings, smart actuators have attracted increasing attention in different application fields, such as artificial muscles, smart textiles, smart sensors, and soft robots. Among these intelligent material, functional hydrogels with fiber structure are of great value in the manufacture of smart actuators. In this review, we summarized the recent advances in stimuli-responsive actuators based on functional materials. We emphasized the important role of functional nano-material-based additives in the preparation of the stimulus response materials, then analyzed the driving response medium, the preparation method, and the performance of different stimuli responses in detail. In addition, some challenges and future prospects of smart actuators are reported.

T. Matsushita

T. Matsushita

Teruo Matsushita

T. Matsushita

Teruo Matsushita

T. Matsushita

T. Matsushita