Search

Fine terrain classification is one of the main applications of Synthetic Aperture Radar (SAR). In the multiband fully polarized SAR operating mode, obtaining information on different frequency bands of the target and polarization response characteristics of a target is possible, which can improve target classification accuracy. However, the existing datasets at home and abroad only have low-resolution fully polarized classification data for individual bands, limited regions, and small samples. Thus, a multidimensional SAR dataset from Hainan is used to construct a multiband fully polarized fine classification dataset with ample sample size, diverse land cover categories, and high classification reliability. This dataset will promote the development of multiband fully polarized SAR classification applications, supported by the high-resolution aerial observation system application calibration and verification project. This paper provides an overview of the composition of the dataset, and describes the information and dataset production methods for the first batch of published data (MPOLSAR-1.0). Furthermore, this study presents the preliminary classification experimental results based on the polarization feature classification and classical machine learning classification methods, providing support for the sharing and application of the dataset.

Improving the energy efficiency of such electrotechnological processes as the electroosmotic dehydration and electroplasmolysis of forage grasses is closely related to an increase in the technological component of the current and a decrease in its thermal component, which is a relevant scientific and technical problem. In the mentioned electrotechnological processes, the plant material is an element of an electrical circuit and its electrophysical properties can be reasonably simulated with an electrical equivalent substitution circuit. The goal of this study is to provide an experimental confirmation for the hypothesis about the existence of an asymmetric nonlinear voltage–current characteristic for the stem wall of forage grasses. The basic provisions from the theories of electrical engineering, electrochemistry, biophysics, electrical measurements, experiment design, and statistical methods for the processing of measurement results are used. Analysis of the obtained polarization characteristics makes it possible to state that the stem wall of forage grasses has an asymmetric nonlinear polarization (voltage–current) characteristic and is a constant EMF source, the outer surface of which is positively charged, and the inner surface of which carries a negative charge. The difference of the potentials is 0.5–0.7 V (bromegrass with a humidity of 80%). The rectifying properties of the stem wall are weakened with increasing frequency of electromagnetic oscillations. For instance, at a frequency of 180 Hz, the rectification factor is 0.5. The shape of the polarization characteristic makes it possible to conclude that the current- and moisture-transfer rate is controlled by the inner potential barrier (the stem wall itself), when the "forward" current crosses the stem wall in the direction from its inner to outer surface. The moisture-transfer rate is controlled by the boundary potential barrier (an interface between two phases or a double electrical layer), when the current passes through the stem wall in the "backwards" direction from its outer to inner surface. Therefore, the mentioned potential barrier proves to be shifted towards the outer surface of the stem wall, causing the nonideal so-called valve effect. The established regularities provide a basis for the synthesis of an electrical equivalent substitution circuit for the stem wall and the substantiation of ways to increase the technological component of the current and decrease its thermal effect. [ABSTRACT FROM AUTHOR]

The development and integration of high-performance electronic devices are critical in advancing energy storage with dielectric capacitors. Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (PVTC), as an energy storage polymer, exhibits high-intensity polarization in low electric strength fields. However, a hysteresis effect can result in significant residual polarization, leading to a severe energy loss, which impacts the resultant energy storage density and charge/discharge efficiency. In order to modify the polarization properties of the polymer, a biaxially oriented polypropylene (BOPP) film with linear characteristics has been selected as an insulating layer and combined with the PVTC ferroelectric polarization layer to construct PVTC/BOPP bilayer films. The hetero-structure and polarization characteristics of the bilayer film have been systematically studied. Adjusting the BOPP volume content to 67% resulted in a discharge energy density of 10.1 J/cm3 and an energy storage efficiency of 80.9%. The results of this study have established the mechanism for a composite structure regulation of macroscopic energy storage performance. These findings can provide a basis for the effective application of ferroelectric polymer-based composites in dielectric energy storage. [ABSTRACT FROM AUTHOR]

Accurate modeling is an important aspect for a reliable design, control and optimization of proton exchange membrane (PEM) fuel cell. The mathematical model of PEM fuel cell involves a set of non-linear equations and is considered as multi-variate, multi-modal and non-linear optimization problem having seven unidentified parameters. This paper proposes a new hybrid approach based on weIghted meaN oF vectOrs and Nelder-Mead (INFONM) method for PEM fuel cell parameter extraction. An optimization problem is framed and a sum of squared error (SSE) based objective function is formulated between estimated and experimental voltages. The effectiveness of the developed approach is evaluated on four available benchmark fuel cell data sheets such as NedStack PS6, BCS 500 W, 250 W and Ballard Mark V fuel cell stacks. A fair comparison is presented with well-established algorithms as well as existing literature work to demonstrate the superiority of INFONM. The results reveal that hybrid approach produces better outcomes in terms of accuracy, reliability and effectiveness as compared to other algorithms. Also, the good closeness between the estimated and experimental polarization curves proves that hybrid approach accurately determines unknown parameters. The obtained value of SSE for NedStack PS6, BCS 500 W, 250 W and Ballard Mark V PEM fuel cell stacks are 1.242, 0.0111, 0.317, and 0.619 respectively whereas, the maximum values of percentage voltage deviations are −1.076%, 0.458%, 1.688%, and 2.69% respectively. Furthermore, statistical indices such as mean, minimum, standard deviation, and maximum value of SSE for hybrid approach indicate a least value among all other algorithms which elucidates hybrid approach as more robust and efficient. Additionally, the convergence curves, box plot study and non-parametric test further validate the robustness and reliability of INFONM in identifying unknown parameters of PEM fuel cell. Moreover, a sensitivity analysis considering SOBOL indicators is also presented to provide an illustration of influence of variation in extracted parameters on PEM fuel cell model.

High electric fields affect the diffusion dynamics of atoms on a metal surface, causing biased surface diffusion that possibly leads to the growth of intensively field emitting protrusions and consequent vacuum breakdown (VBD). The scientific understanding of this process, as well as other fundamental VBD initiation mechanisms, is far from complete. Here we investigate the exact atomic behaviour of metal surfaces exposed to extremely high electric fields using density functional theory (DFT). Previous theories describe the field-surface dynamics in terms of the effective dipole moments and polarizability of surface atoms, disregarding higher-order (hyperpolarizability) terms. The validity of this approximation has been evaluated only for electric fields up to 3 GV/m, due to computational limitations of the plane-wave DFT basis used in previous works. In this work, we test the validity of this approximation for a much wider field range, relevant for VBD and field emission (FE), using Cu nanoparticles as our test structures. We find that although such high fields can change the entire structure of Cu nanoparticles, their energetics are described very precisely by the permanent dipole moment and polarizability terms. Thus, we show that neglecting the hyperpolarizability terms is valid even for field values that exceeds the range that is relevant for intense FE and VBD. This work lays a solid foundation for further developing atomic-level simulation models for electric field-induced surface diffusion on metal surfaces and its effects on protrusion growth and VBD initiation. [ABSTRACT FROM AUTHOR]

Although button solid oxide fuel cells (SOFCs) have been extensively used in fundamental research, practical commercial applications are developed on industrial-sized SOFCs. As the active area and fuel utilization increase, some issues that are not considered in button cells become essential. Therefore, it is necessary to focus on the differences between button cells and industrial-sized cells, including their polarization characteristics and performance evaluation. In this study, the polarization curves of both types of cells under different hydrogen flow rates are tested. Both types of cells experience a sudden increase in total area-specific resistance (R tot) under high current density. However, the effects of hydrogen flow rate differs between cell types. Based on the equivalent circuit model (ECM) fitting of electrochemical impedance spectroscopy (EIS) measured under different DC biases and the theoretical calculation of gas diffusion and gas conversion resistances, it is demonstrated that the rapid increase in R tot in button cells is primarily attributed to gas diffusion through the anode. In contrast, non-uniform gas distribution along the flow channel direction results in a dominant role of gas conversion resistance on R tot in industrial-sized cells, especially at hydrogen flow rates below 0.4 L min−1. Although electrical efficiency is often overlooked in button cells, it is a crucial performance evaluation index in industrial-sized cells. The impact of operating parameters on power density and electrical efficiency is analyzed, revealing a trade-off between the two. With the critical Nernst electromotive force of Ni oxidation as the voltage lower limit, the optimal operating conditions with high electrical efficiency and prevention of Ni oxidation under different flow rates are obtained. It is investigated that operation should be carried out at a low flow rate below 0.3 L min−1 to achieve high electrical efficiency of over 50%. The selected operating parameters will change when the cell performance or load demand changes. However, the analysis method proposed in this paper can still provide a reference for selecting the operating parameters of a SOFC system. • Comparison of polarization characteristics between button and industrial-sized SOFCs. • Dominant process of polarization in industrial-sized cells varies at different flow rates. • High voltage at high fuel utilization with low flow rate prevents Ni oxidation. [ABSTRACT FROM AUTHOR]

Transmittance is an important evaluation parameter of display equipment. High transmittance has better effects both on power dissipation and subjective visual feeling of image. In this paper, we reported a brand new method to simulate the transmittance considering the polarization characteristics of backlight unit. The new method optimized the test method of polarization characteristics of backlight unit, put forward an algorithm that can transfer polarization characteristics into parameters of polarizer database in Techwiz, changed the simulation way of Techwiz. [ABSTRACT FROM AUTHOR]

Detection of underwater coherent interference is necessary as its presence affects the estimation of the desired target. In this work, a method based on high-order particle velocity gradient polarization characteristics is proposed to distinguish the presence of coherent interference. Characteristics including ellipse ratio and inclination angles of the high-order particle velocity gradient are chosen as effective detection features because they remain unchanged at different orders of the desired target but changed at different orders of coherent signals when there is coherent interference. Based on such altered properties, a quick and effective marine detection system can be established. Both simulation and experimental results validate the proposed detection method. [ABSTRACT FROM AUTHOR]

In marine target detection, sun glint is a strong source of interference, which causes a large area of pixel saturation during imaging, making it difficult to effectively distinguish between the target and the sea surface background. To address the problem of sun glint interfering with target imaging, we first simulate and analyze the multi-angle polarization characteristics of rough sea surface seawater according to the Cox–Munk rough sea surface probabilistic statistical model. Secondly, we propose the constraints that the refracted light information of seawater can be effectively separated at the near-horizontal observation zenith angle, and the polarization orthogonal decomposition principle is utilized to realize the separation of reflected and refracted light of seawater. Finally, we refer to the underwater imaging model and propose an equivalent model of target imaging under sun glint interference. The light intensity information of the sea surface background and the target is equivalently replaced by the light intensity information of the reflected and refracted light of seawater, which further solves the target image without the interference of sun glint. The results show that our method not only realizes the enhancement of the target image based on the suppression of the sea surface sun glint, but also preserves the texture information of the sea surface. The method is of great practical significance for the search and rescue of people overboard as well as the monitoring of marine ecological environment. • Proposing constraints for effective separation of seawater refracted light. • Proposing an equivalent model of target imaging under sun glint interference. • Enhancement of sea surface target images based on suppression of sun glint. [ABSTRACT FROM AUTHOR]

Electroluminescence is a defect detection method commonly used in photovoltaic industry. However, the current research mainly focuses on qualitative analysis rather quantitative evaluation, since there exists some shortcomings, such as fuzzy edges, unclear texture, etc., in the obtained electroluminescence images. Electroluminescence polarization imagery is a new method for defect detection in photovoltaic modules, which can effectively make up for the aforementioned deficiencies. In this paper, the polarization characteristics and formation mechanism of silicon solar panels was investigated based on the principle of electroluminescence. Firstly, the polarization imaging mechanism of electroluminescence of photovoltaic modules was studied. Then, an electroluminescence polarization experimental platform was built, and the polarized electroluminescence images of photovoltaic panels were obtained and preprocessed with Gaussian filter. Finally, the influence of view angle, bias voltage and other factors on the polarization characteristics was discussed. The results show that the electroluminescence of photovoltaic modules has polarization characteristics, and the degree and angle of polarization are related to the view angle and bias voltage; the degree of polarization of photovoltaic panel electroluminescence increases with the angle of view, and first increases then rapidly decreases with bias voltage. [ABSTRACT FROM AUTHOR]

Zhao, S.; Gu, D.; Guo, C.; Wang, X., and Zhang, J., 2023. Propagation characteristics of seismic waves in shallow sea sedimentary layers. Journal of Coastal Research, 39(1), 32–44. Charlotte (North Carolina), ISSN 0749-0208. To explore new techniques for detecting and identifying targets in water, the propagation characteristics of seismic waves in shallow sea were deeply studied. Wave theory and staggered grid finite difference method were employed to analyze the propagation characteristics of seismic waves in a layer of underwater medium with a sedimentary layer. The results show that a Scholte wave is prone to disperse in an underwater medium with a sedimentary layer. The sediment thickness and acoustic parameters have great influence on the propagation characteristics of seismic waves. Moreover, the seismic wave signals were mainly concentrated below 20 Hz by collecting the vibration velocity of underwater interface. Furthermore, Scholte wave signals in underwater experiments were determined by utilizing four filtering methods and Scholte polarization characteristics, and the Butterworth filtering method can better preserve the integrity of vibration velocity signal. The theoretical, numerical, and experimental polarization characteristic results are basically consistent, which indicate that Scholte wave can be well extracted by the method of polarization characteristics. [ABSTRACT FROM AUTHOR]

We propose a polarized image defogging algorithm according to the sky segmentation results and transmission map optimization. Firstly, we propose a joint sky segmentation method based on scene polarization information, gradient information and light intensity information. This method can effectively segment the sky region and accurately estimate the global parameters such as atmospheric polarization degree and atmospheric light intensity at infinite distance. Then, the Gaussian filter is used to solve the light intensity map of the target, and the information of the polarization degree of the target is solved. Finally, based on the segmented sky region, a three-step transmission optimization method is proposed, which can effectively suppress the halo effect in the reconstructed image of large area sky region. Experimental results shows that defogging has a big improvement in the average gradient of the image and the grayscale standard deviation. Therefore, the proposed algorithm provides strong defogging and can improve the optical imaging quality in foggy scenes by restoring fog-free images. [ABSTRACT FROM AUTHOR]

• Nonionic surfactant Polysorbate-20 (PS20) was adopted to control crystallization and growth of CsPbBr x I 3-x perovskite. • PS20 modified CsPbBr x I 3-x perovskite film exhibited smooth morphology and enhanced radiative recombination. • The modified perovskite behaved better ASE performance with a threshold of 4.72 μJ/cm2 and a gain factor of 1252 cm−1. All-inorganic perovskites have become promising optical gain medium due to excellent optical properties. For CsPbX 3 thin films, optical losses caused by uneven morphology and non-radiative defects can hinder amplified spontaneous emission (ASE) performance. Here, we take advantage of additive engineering strategy to simultaneously control the morphology and defect states of CsPbBr x I 3-x films via introducing Polysorbate-20 (PS20) into perovskite precursor. The optical gain coefficient of the CsPbBr x I 3-x film increased from 491.1 cm−1 to 1252 cm−1 and ASE threshold decreased to 4.72 μJ/cm2. Moreover, the optimized perovskite film exhibited excellent linear polarization characteristics with high degree of polarization (DOP) of 88 %. Our research highlights the importance of defect passivation and morphology control to improve ASE performance. [ABSTRACT FROM AUTHOR]

As a kind of basic facility in oil and gas exploitation, the deep well casing is often subjected to corrosion. Cathodic protection (CP) is an important technology to mitigate the corrosion of the deep well casing. However, the casing works in a deep well thousands of meters deep underground and passes through different stratigraphic structures with various soil environments. Besides this, in a casing well group including multiple casings, there are interactions between different casings. These problems make it difficult to design the anode groundbeds for the CP of the deep well casings and evaluate the effectiveness of CP system. Therefore, the optimization of anode groundbeds for CP of deep well casings was studied based on the boundary element method in this paper. The polarization behaviors of steel casing in different depths were measured in the field. And then the mathematical model for the CP of the deep well casing was built based on the geometric structure of casing, stratified soil resistivity, and polarization characteristics. The optimum design parameters of anode groundbeds for casing CP were explored by a numerical simulation with the boundary element method to provide a reference for the design and evaluation of CP systems for deep well casings. [ABSTRACT FROM AUTHOR]

Polarization is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. This paper proposes a method for detecting small targets on the sea surface based on the combination of polarization features of two models. The scattering mechanism of sea clutter is random scattering at low glazing angle or glancing angle and the randomness is high as the angles do not have any specified shape. However, a target has a specific shape, and thus, the randomness of scattering will be less. Clutter is a term used for unwanted echoes in electronic systems, particularly in reference to radars. Such echoes typically return from ground, sea, rain, and animals/insects. In this literature, the randomness of a scattering mechanism in an echo is obtained from the probability density functions of polarization entropy using the Cloude decomposition model. Further, the proportion of scattering at spherical, dihedral, and helicoid angles from the target echoes will be different in the sea clutter. Therefore, the relative coefficient of power of these three scattering components in each echo is extracted based on Krogager polarization decomposition. Then, polarization features with good separability and complementarity are selected to form the polarization feature vector, and the characteristics are verified by Principle Component Analysis (PCA). Finally, One Class Support Vector Machine (OCSVM) is used for classification and recognition based on the polarization decomposition feature vector. Instead of single-polarization detection methods, our method uses two polarization modes to extract the decomposition features with separability and complementarity through polarization coherent decomposition and incoherent decomposition, respectively. The experimental results of the IPIX data show the effectiveness of our method. Thus, the detection performance of our model is better than those methods based on single-polarization decomposition in complex and difficult sea conditions.

Detection of underwater coherent interference is necessary as its presence affects the estimation of the desired target. In this work, a method based on high-order particle velocity gradient polarization characteristics is proposed to distinguish the presence of coherent interference. Characteristics including ellipse ratio and inclination angles of the high-order particle velocity gradient are chosen as effective detection features because they remain unchanged at different orders of the desired target but changed at different orders of coherent signals when there is coherent interference. Based on such altered properties, a quick and effective marine detection system can be established. Both simulation and experimental results validate the proposed detection method.

Visible light polarization image desmogging aims to recover the clear image solely from an input visible light polarization image with smog. It is a challenging research topic due to desmogging is an ill-posed problem. Most of existing methods effort to build desmogging physical model based on classical atmospheric scattering principle. However, compared with natural image dehazing task, the smog in visible light polarization image is very complex and diverse, which makes it hard to find accurate desmogging physical model. To address this issue, we propose a Cycle Convolutional Neural Network (CCNN), which exploits polarization characteristics explicitly to learn a visible light polarization image desmogging model in an end-to-end way. To be specific, the model computes polarization information of the visible light polarization image via Stokes equation. Object detection sub-network is utilized to detect smog regions according to the polarization information. Then an encoder–decoder sub-network with feature converter structure is proposed to generate smog-free regions. The coarse clear image is obtained by fusing the generated smog-free regions with original smog visible light polarization image. More importantly, to obtain the final clear image, the coarse clear image is considered as the input data to our model again, which makes our model in a cycle topology. Moreover, we contribute the first large-scale dataset for visible light polarization image desmogging evaluation, which contains 17,216 visible light polarization images, to validate our proposed method. On this dataset, extensive experiments demonstrate that our method can achieve the best performance in comparison with the state-of-the-art baselines. [ABSTRACT FROM AUTHOR]

A transmissive metasurface polarization beam splitter (MPBS) with three-layer dielectric substrate was designed to meet the application requirements of polarization beam splitting devices. The microstructure unit cell was composed of an elliptical patch and a square resonant ring, and the phase and amplitude responses to the x- and y-polarized incident waves were independent. Here 16 transmissive unit cells designed with a 90° phase difference and more than 0.8 transmission coefficient could be used to realize different functions by pre-designing distribution of "00", "01", "10", "11" encoding particles in x- and y-direction. We experimentally demonstrated a 2-bit encoding MPBS that separated x- and y-polarization incident waves into two different directions at 15 GHz respectively using specially designed encoding unit cells. The work may alleviate the shortage of advanced multifunctional devices and provide important application prospect in imaging, MIMO system, etc. [ABSTRACT FROM AUTHOR]

Electroluminescence is a defect detection method commonly used in photovoltaic industry. However, the current research mainly focuses on qualitative analysis rather quantitative evaluation, since there exists some shortcomings, such as fuzzy edges, unclear texture, etc., in the obtained electroluminescence images. Electroluminescence polarization imagery is a new method for defect detection in photovoltaic modules, which can effectively make up for the aforementioned deficiencies. In this paper, the polarization characteristics and formation mechanism of silicon solar panels was investigated based on the principle of electroluminescence. Firstly, the polarization imaging mechanism of electroluminescence of photovoltaic modules was studied. Then, an electroluminescence polarization experimental platform was built, and the polarized electroluminescence images of photovoltaic panels were obtained and preprocessed with Gaussian filter. Finally, the influence of view angle, bias voltage and other factors on the polarization characteristics was discussed. The results show that the electroluminescence of photovoltaic modules has polarization characteristics, and the degree and angle of polarization are related to the view angle and bias voltage; the degree of polarization of photovoltaic panel electroluminescence increases with the angle of view, and first increases then rapidly decreases with bias voltage.

Copyright of Journal of National University of Defense Technology / Guofang Keji Daxue Xuebao is the property of NUDT Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a road detection and tracking technique using polarization characteristics of the road in the long-wave infrared (LWIR) spectrum. Conventional vision-based road detection techniques often apply color and texture information, which tend to underperform in low illumination conditions at night. The Division of Focal Plane (DoFP) infrared polarization imaging technology enables real-time acquisition of polarization characteristics of the road with a monocular camera for day-and-night operation. The polarization characteristics of the road in LWIR embody zero-distribution of Angle of Polarization (AoP) in the road region and the difference of Degree of Polarization (DoP) between the road and vehicles. A road detection and tracking scheme is proposed using the difference in polarization characteristics in LWIR between the road region and the background, along with the intensity and temporal information. We also built a LWIR DoFP Dataset of Road Scene (LDDRS) consisting of a total of 2,113 images annotated manually. Experiments on the LDDRS database demonstrate that the proposed method outperforms two state-of-the-art real-time semantic segmentation networks, FANet-34 and SwiftNet, by 1.4% and 2.1% in terms of IoU, respectively. [ABSTRACT FROM AUTHOR]

A Hollow-core Anti-resonant Fiber (ARF) has many advantages in device applications, such as low cladding density, low nonlinearity, high damage threshold, and excellent polarization characteristics by adjusting the structure and filling a metal. A method of on-line copper coating on the inner hole of hollow-core anti-resonant fiber cladding during drawing is proposed in this paper, and the related polarization characteristic of the ARF is studied. The theoretical and experimental results show that the ARF has good polarization characteristics after coating due to the coupling of copper film and core mode. Polarized light at 860 nm shows the best polarization characteristics. When the ARF is 1 mm, 1.5 mm, and 2 mm in length, its crosstalk is more than 20 dB which works well in communications applications. These characteristics indicate that the ARF coated copper film has a good application prospect in the field of polarization communication.

The paper considers methodological issues of solving the inverse problem of electromagnetic sound, based on the results of measuring the low-frequency magnetic field from two orthogonal antennas located on the Kola Peninsula in areas with different conductivity of the lithosphere. The polarization characteristics of the tangential magnetic field components are determined. They are compared with theoretical calculations using a plane-layered model of a wave propagation medium with homogeneous layers. Comparison of the theoretical calculations with the experimental data on the major axis of the polarization ellipse yields results consistent with existing concepts of the conductivity of the Kola Peninsula. Differences in the direction of the ellipse and ellipticity require complication in the model: the inclusion of faults in the lithosphere, as well as the anisotropy of the structures forming it. [ABSTRACT FROM AUTHOR]

This paper studied the correlation characteristics of the polarization backscattering matrix of the dense chaff cloud with uniform orientation and location distributions in circular symmetry region. Based on the theoretical analysis and numerical experiments, the correlation coefficients of the four elements in the polarization backscattering matrix are obtained, and the results indicate that the cross to co-polar correlation coefficient is still zero; and that the sum of the co-polar cross-correlation coefficient and the two times of linear depolarization ratio equals one. The results are beneficial for better understanding of the backscattering characteristics of dense chaff clouds, and are useful in the application of jamming recognition in radar electronic warfare. Numerical experiments are performed by using the method of moments.

A Hollow-core Anti-resonant Fiber (ARF) has many advantages in device applications, such as low cladding density, low nonlinearity, high damage threshold, and excellent polarization characteristics by adjusting the structure and filling a metal. A method of on-line copper coating on the inner hole of hollow-core anti-resonant fiber cladding during drawing is proposed in this paper, and the related polarization characteristic of the ARF is studied. The theoretical and experimental results show that the ARF has good polarization characteristics after coating due to the coupling of copper film and core mode. Polarized light at 860 nm shows the best polarization characteristics. When the ARF is 1 mm, 1.5 mm, and 2 mm in length, its crosstalk is more than 20 dB which works well in communications applications. These characteristics indicate that the ARF coated copper film has a good application prospect in the field of polarization communication. [ABSTRACT FROM AUTHOR]

The proton exchange membrane water electrolyzer has garnered increasing attention for the large-scale consumption of intermittent renewable energy to produce high purity "green hydrogen", contributing to the realization of futural carbon neutrality goals. The necessity of control-oriented polarization characteristic modeling with accurate parameter identification remains a significant challenge for the performance evaluation of this type of water electrolyzer. In this paper, an improved control-oriented polarization characteristic modeling for proton exchange membrane water electrolyzer with adaptive hunting game based metaheuristic optimization is proposed to foster collaborative performance enhancement between model improvement and optimizer investigation. The inspiration behind model improvement lies in the nonlinear mechanism linkage between partial pressures of liquid water supplying and anode gas separator. Then, an adaptive hunting game based metaheuristic optimizer is proposed to address the inherent local multi-extremum distribution problem in the established model. Experimental data from a commercial water electrolyzer system is used to validate the effectiveness and practicability of the proposed model-optimizer pair. Detailed comparisons reveal that the improved model development, with its consideration of critical mechanisms, ensures enhanced metaheuristic efficiency in the designed optimizer, both in terms of robust intensity evaluation and efficient quasi-Newton based local search. Statistically, the collaboration performance enhancement reaches up to 7.33% when compared with the other model-optimizer. • The polarization characteristic model for PEMWEs is improved mechanistically. • An adaptive hunting game-based metaheuristic optimizer is proposed. • Enhanced metaheuristic efficiency is guaranteed for the proposed optimizer. • Collaborative performance of the proposed model-optimizer pair is improved. [ABSTRACT FROM AUTHOR]

To deal with the large error of burst height measurement for novel optional burst height millimeter wave proximity fuses in new-generation long-range projectiles, a ground object recognition strategy based on echo polarization is proposed in this paper. In the height measurement process, there are many factors, including the flight condition of the projectile, tall objects, ground clutter, interference signals, etc. restricting measurement accuracy. Therefore, a novel measurement scheme is urgently needed to enhance the accuracy of height measurements. The method mainly distinguishes the surface and ground objects within the range of the detected beam, under the condition that the detection area has apparent divisions. The polarimetric rotation-invariant parameters are used to analyze the features of ground objects. On the other hand, when the detection area does not have apparent divisions, the polarimetric echo reconstruction technology is used to determine the surface. Simulation experiments show the feasibility and superiority of the proposed method compared with the traditional height measurement system. Even in the presence of extensive interference, the method allows the accurate measurement of the projectile's height above the ground. [ABSTRACT FROM AUTHOR]

Meteorological target simulation using polarization information is the foundation of the theoretical research and design application of dual-polarization Doppler weather radar. Currently, the theoretical research of airborne dual-polarization weather radar is in the development stage. To provide high-fidelity simulation data required for airborne dual-polarization weather radar detection technology, in this study, a simulation method of the polarization characteristics of rainfall determined using airborne weather radar based on numerical weather prediction is proposed. The numerical weather prediction model is used to realize the modeling and simulation of meteorological scenarios and provide information on meteorological parameters such as temperature, particle concentration, and mixing ratio of rainfall. In the analysis of the microphysical properties of rainfall, the electromagnetic scattering matrix is calculated and the simulation of the polarization characteristics of rainfall is achieved. The simulation results for different microphysical property parameters have led to the establishment of a high-fidelity rainfall model and demonstrated (via comparison with the real radar data) that the simulation of polarization characteristics using the proposed method is effective and reliable.

Nd-Fe-B permanent magnets doped with CuZn powders were prepared via conventional sintered method. The effects of CuZn contents on magnetic properties and corrosion resistance of the magnets were systematically studied. It shows that the remanence, coercivity, and maximum energy product decrease gradually with the increase in CuZn doping content. The magnet's corrosion kinetics in autoclaves environment and its electrochemical properties in electrolytes were also examined. It is interesting to see that the weight loss of 3.5 wt% and 4.5 wt% CuZn powders doping magnets is only 1 and 0 mg·cm after autoclaves test at 121 °C, 2 × 10 Pa for 500 h, respectively, which is much lower than that of the magnets without CuZn doping. Electrochemical results show that the CuZn powders doping magnets display more positive corrosion potential ( E ) and lower corrosion current density ( I ) than those of the original magnets without CuZn doping in sulphuric acid electrolyte and distilled water. It is, therefore, concluded that doping CuZn powders is a promising way to enhance the corrosion resistance of sintered Nd-Fe-B magnets. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) detection is commonly used in the failure diagnostics of the gas insulated switchgear (GIS) with the basin-type insulator. We recognized that the polarization plays an important role in the PD detection. In this paper, we present both theoretical and experimental investigations on the polarization characteristics of the electromagnetic (EM) wave leakage in GIS with metal belt and the electric field intensity distribution near the GIS aperture. The characteristics of the three electric field components around the aperture are simulated by using software Ansoft HFSS. Experiments are also conducted to verify the theoretical results. Both the simulation and the experiment show that near the aperture the electric field component along the GIS axis is always dominant for the typical configuration under study. For an efficient detection it is therefore advised to use linear antenna sensor placed along the GIS axis. [ABSTRACT FROM PUBLISHER]

This paper presents an analysis of the study of the polarized component of the reflectance factor ( R) and the degree of polarization ( P) of wheat and maize crops depending on the wavelength. The polarization characteristics were obtained in the field from an elevated work platform at heights of 10 to 18 m in June and July. Measurements were performed using a double-beam spectrophotometer with a polarized light filter attachment within the spectral range from 400 to 820 nm. The viewing angle was no greater than 20° with respect to the nadir. The reflection spectra of wheat and maize crops that were obtained using a polarizer adjusted to transmit the maximum and minimum amounts of light ( R and Rn) were studied. Based on these reflection spectra, the polarization characteristics, which differ in the visible and infrared spectral regions, were determined and analyzed. [ABSTRACT FROM AUTHOR]

The main purpose of this project has been to simulate the behavior of a PEM-type fuel cell working in a stationary regimen using an equivalent circuit (EC). The EC designed with Multisim circuit design software reproduces the three characteristics sections of a polarization curve for a proton exchange membrane fuel cell (PEMFC). The main characteristic of this EC is that it offers the possibility to adapt the power range of the fuel cell in the simulated electronic model. To do so, a transconductance is used to allow adjusting the load current range. The EC allows fitting the simulated results to any commercial PEM fuel cell polarization curves and power ranges, adjusting parameters such as the charge current I FC and the reversible voltage of the PEM fuel cell E rev , and then setting the resistor values in the losses blocks and in the amplifiers. Validation of the EC has been performed by simply adjusting the empirical data obtained with an Electrochem commercial 25 cm 2 active area PEMFC to the different analog blocks of the EC. Adjustments were carried out by using Mathcad 14 calculation algorithms. [ABSTRACT FROM AUTHOR]

The polarization characteristics of the multifunctional integrated optic chip (MFIOC) are fully evaluated with high accuracy by using optical coherence domain polarimetry based on white light interferometer. Two polarization maintaining (PM) fibers, serving as extended fibers, are spliced to the PM pigtails of the MFIOC with polarization axes aligned. By launching light at 45° to the birefringence axes of the lead-in extended PM fiber, the beams along the fast and slow axes of the birefringent waveguides interfere after a 45° polarization analyzer and an optical path correlator. The polarization extinction ratio (PER) and birefringence of the LiNbO3 Y-waveguide, the birefringence of the PM pigtails, and the crosstalks at the connection points between the Y-waveguide and the PM pigtails can be simultaneously obtained from the amplitudes and positions of the corresponding interference peaks. The characteristic peak of the Y-waveguide's PER is shifted out of the interference peak of the light source ripple by selecting proper length of the extended fibers. The extended fibers also brings in two additional cross-coupling points at the ends of the PM pigtails, which are used for calculating the birefringence of the PM pigtails. In addition, the alignment type between the PM pigtails and the birefringent Y-waveguide is identified according to the position of the characteristic peak of the Y-waveguide's PER. Theoretical model based on Jones matrix is built to describe the characteristic peaks of the MFIOC. Two MFIOCs with different alignment angle between the PM pigtails and the Y-waveguide are experimentally tested. Results show that the PER resolution of the proposed method can achieve nearly -90 dB and the dynamic range of the test system is about 90 dB. [ABSTRACT FROM PUBLISHER]

A TE-pass polarizer with cylinder array inserted in buffer layer of silica-on-silicon waveguide (CABL-WG) is proposed. The polarization characteristics of the CABL-WG are analyzed by means of the full vectorial finite element method at a wavelength of 1550 nm, where the low loss of TE fundamental mode could be made while the TM fundamental mode has very large leakage loss. The optimization design for the polarizer with ultralow insertion loss of 0.07 dB and high extinction ratio of 38.94 dB is given. [ABSTRACT FROM PUBLISHER]

Abstract: Polarization curves for the porous lithiated NiO cathode are very often reported with a linear slope over a wide potential range. However, the MCFC behaviour at higher oxidant utilization, when the mass transfer becomes dominant, is mostly overlooked. Therefore, in this study, the two most common cathode mechanisms are utilized to compare their prediction capabilities at higher current densities. This is performed by means of a three-dimensional, non-isothermal mathematical model which is developed by employing volume-averaged equations. As an extension to previous studies, the presented model also considers the potential and current density variation in both solid electrode and liquid electrolyte phases. In essence, this model is a set of partial differential equations including conservation of mass, momentum, gaseous species, energy, electronic potential and ionic potential that are solved using a finite volume method. In brief, both peroxide and superoxide mechanisms predict the linear region of the polarization curve accurately. However, none of these mechanisms showed a downward bent in the polarization curve. A positive exponent for the oxygen mole fraction is essential in obtaining the downward bent knee at high current densities which is in contrast to what has been reported in the literature to-date. [Copyright &y& Elsevier]

Abstract: In view of using only the intensity information of retroreflection wave and poor capacity of anti-interference in laser short-range detection, this paper analyzes the polarization characteristics of laser beam on the metal surface and establishes reflection model of polarized laser. A target detection method based on polarization characteristics of reflection laser is putted forward and the simulation of polarization characteristics on the surface of several typical metal targets is implemented at last. [Copyright &y& Elsevier]

Abstract: Based on the extended Huygens–Fresnel principle and the unified theory of coherence and polarization, the analytical expressions for the elements of the cross-spectral density matrix, the degree of polarization and the degree of coherence of partially coherent elegant Laguerre–Gaussian (PCELG) beams in non-Kolmogorov turbulence have been derived. An investigation of the changes in the on-axis spectral degree of polarization (SDP) and in the spectral degree of coherence (SDC) of PCELG beams for different beam parameters and turbulence parameters propagating in non-Kolmogorov turbulence are specifically illustrated by numerical examples. [Copyright &y& Elsevier]

Property distribution and polarization characteristics of a proton exchange membrane fuel cell (PEMFC) under cathode starvation conditions were investigated numerically and experimentally for a unit cell. The polarization curves of a lab-scale PEMFC were measured with increasing current density for different cell temperatures (40°C, 50°C, and 60°C) at a relative humidity of 100%. To investigate the local temperature, water content and current density on the membrane, and gas velocity in the channel of the PEMFC, numerical studies using the es-pemfc module of the commercial flow solver STAR-CD, which were matched with experimental data, were conducted. Temperature, current density on the membrane, and water content in the MEA were examined to investigate the effect of cell temperature on performance under the cathode starvation condition. At cathode starvation conditions, the performance of a higher cell temperature condition might drop significantly and the mean temperature on the membrane increase abruptly with increasing cell temperature or current density. Copyright © 2009 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Multi walled carbon nanotubes (MWNTs) have been synthesized by chemical vapour deposition technique using AB3 alloy hydride catalyst. Platinum supported MWNTs (Pt/MWNTs) and platinum-tin supported MWNTs (Pt–Sn/MWNTs) electrocatalysts have been prepared by chemical reduction method. MWNTs and electrocatalysts have been characterized by powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), high resolution TEM (HRTEM) and Energy dispersive X-ray analysis (EDAX). The anode and cathode electrodes for DEFC have been fabricated using Pt–Sn/MWNTs and 1:1 Pt/MWNTs + Pt/C electrocatalyst respectively. Performances of Direct Ethanol Fuel Cell (DEFC) with these electrodes have been studied at different temperatures of the membrane electrode assembly at ambient fuel conditions and the results have been discussed. A maximum power density of 38.6 mW/cm2 at a current density of 130mA/cm2 is obtained. A six cell planar Micro Direct Ethanol Fuel Cell (μ-DEFC) stack was also constructed using these electrocatalysts and etched printed circuit boards as anode and cathode current collectors. A maximum power density of 2 mW/cm2 was achieved when the μ-DEFC was operated in air breathing mode at room temperature. This enhancement of the performance may be attributed to dispersion and accessibility of MWNTs support and Pt–Sn in the electrocatalyst mixture for ethanol oxidation reaction. [Copyright &y& Elsevier]

Abstract: In this work, a radome was fabricated using a composite sandwich constructions composed of an E-glass fabric/epoxy composite, a PVC foam, and a frequency selective surface (FSS) for stealth performance. The polarization characteristics of the stealth radome were investigated using measured electromagnetic (EM) transmission characteristics with respect to the polarization angle between the direction of the electric field of incident EM waves and the direction of the dipole length by way of a free space measurement system. The dielectric properties of the E-glass fabric/epoxy composite and the PVC foam were also measured with respect to the polarization angle. [Copyright &y& Elsevier]

In order to improve the electromagnetic environment associated with the widespread use of electronic devices for communication, computation, automation, among other purposes, the present paper has developed a carbon plate that exhibits polarization characteristics. To achieve polarization characteristics in the far field, slits were cut into the surface of a carbon plate; termed the slit carbon plate. The value of the RF magnetic shielding degree SDHP when holding the slits of the carbon plate perpendicular to the ground, in the frequency region of 140 MHz to 700 MHz, increased with frequency, and displayed a value of 35 dB at 700 MHz. It was also shown that the value of SDHH, when aligning the slits horizontal to the ground, increased with frequency, and recorded a value of 5 dB at 700 MHz. Namely, the difference in the shielding degrees of the slit carbon plate for the orientation of the slits indicated polarization characteristics. In present research, the polarization characteristics of the slit carbon plate were improved, in the frequency region of 1 MHz to 800 MHz, by the superposition of slit ferrite and copper plates over the slit carbon plate; termed compound plate. For example, the difference between the values of SDHP and SDHH for the compound plate at 30 MHz was found to be improved by approximately 50 dB. In addition, important criteria are discussed for the design of a plate having polarization characteristics, for effective RF magnetic shielding. [ABSTRACT FROM AUTHOR]