DOA Estimation of Cylindrical Conformal Array Based on Geometric Algebra

Due to the variable curvature of the conformal carrier, the pattern of each element has a different direction. The traditional method of analyzing the conformal array is to use the Euler rotation angle and its matrix representation. However, it is computationally demanding especially for irregular array structures. In this paper, we present a novel algorithm by combining the geometric algebra with Multiple Signal Classification (MUSIC), termed as GA-MUSIC, to solve the direction of arrival (DOA) for cylindrical conformal array. And on this basis, we derive the pattern and array manifold. Compared with the existing algorithms, our proposed one avoids the cumbersome matrix transformations and largely decreases the computational complexity. The simulation results verify the effectiveness of the proposed method

Statistical Analysis of High-Resolution Coherent Monopulse Radar Sea Clutter

A statistical analysis that properly characterizes sea clutter processes is indispensable both for optimum detection algorithm design and for performance prediction problems in maritime surveillance applications. In this paper, we present the statistical analysis of experimental sea clutter data collected by a high-resolution coherent monopulse radar. First, we present the amplitude statistical analyses for these clutter data. The results show that the K, Pareto, and CIG distributions can each provide good fits to the clutter data for three channels of monopulse radar. The analyses on the variations of the K distribution parameters with range suggest that the scale parameter is closely associated with the clutter powers and that the shape parameter is influenced by the sea state. Then, we focus on the correlation properties. The averaged results suggest that the temporal and spatial correlation properties are similar for the clutter of all three channels. Moreover, the clutter between the sum and difference channels is almost completely correlated in elevation and is lowly correlated in azimuth. Finally, we perform a spectral analysis, highlighting the temporal and spatial variabilities of Doppler spectra. It is found that the individual Doppler spectra in all three channels can be represented by Gaussian-shaped power spectral densities, and their centroid and width can be modeled as two separate stage linear functions of spectrum intensity

Suppression of Cross-Polarization of the Microstrip Integrated Balun-Fed Printed Dipole Antenna

The high cross-polarization of the microstrip integrated balun-fed printed dipole antenna cannot meet the demands of many engineering applications. This kind of antennas has high cross-polarization levels (about −20 dB). And we find that the high cross-polarization radiation is mainly produced by the microstrip integrated balun rather than the dipole itself. The very limited method to lower the cross-polarization level of this kind of antennas is to reduce the substrate thickness. In this paper, to improve the low cross-polarized performance, firstly, an equivalent model is presented to analyze the cross-polarization radiation. Secondly, a novel structure with low cross-polarization is proposed. The microstrip integrated balun is enclosed by a center slotted cavity. The E-field of the microstrip integrated balun is transformed parallel to the dipole arms by the slot, so the radiation of the cross-polarized component is suppressed. Measured results show that this structure can achieve a bandwidth wider than 40% while reducing the cross-polarization level to less than −35 dB within the frequency band

Overnutrition-induced gout: An immune response to NLRP3 inflammasome dysregulation by XOD activity increased in quail

BackgroundGout is a progressive metabolic disease closely related to hyperuricemia and urate deposition, with an increasing prevalence and incidence across the globe. Recent studies have shown that the pathological process of gout includes two stages: asymptomatic hyperuricemia and MSU crystal deposition. However, the immune response during the development of hyperuricemia to gouty arthritis is not fully elucidated.MethodsThus, an overnutrition-induced whole-course gout model was established to clarify the immune response and pathological changes in the development from hyperuricemia to gouty arthritis. The quails without urate oxidase were used as experimental animals. And we confirmed that uric acid metabolic targets were changed when quails were in the asymptomatic hyperuricemia stage. ResultsWhen the quail showed gout symptoms, the NLRP3 inflammasome was activated, and the expressions of IL-1β, TNF-α, IL-6, IL-8, and IL-18 were significantly increased. The relationship between the uric acid metabolism target and the NLRP3 inflammasome may be the critical immune response between hyperuricemia and gouty arthritis. Our data showed that, in the process of gout disease, the expression of xanthine oxidase (XOD) has been increasing, which increases the level of uric acid, disrupts the balance of oxidative stress, generates a large amount of ROS, activates the NLRP3 inflammasome, and release IL-1β. Treatment with the XOD inhibitor can reduce uric acid, restore the body’s degree of peroxidative damage and antioxidant capacity, and inhibit NLRP3 inflammasome and IL-1β. In vitro, we extracted and identified primary fibroblast-like synoviocytes (FLS) from quail for the first time. Stimulating FLS with uric acid also caused ROS release and NLRP3 inflammasome activation. However, treatment with an XOD inhibitor prevented all these responses in FLS. ConclusionOur results indicate that the immune response between the uric acid metabolism target XOD and NLRP3 inflammasomes plays a crucial role in developing hyperuricemia to gouty arthritis, and inhibition of both XOD and NLRP3 inflammasomes may be an effective treatment for avoiding the development of asymptomatic hyperuricemia to MSU crystal deposition. Meanwhile, this study also provides an advantageous animal model for pathological mechanisms and research and development drugs for gout

Identifying the Species of Seeds in Traditional Chinese Medicine Using DNA Barcoding

Seed is not only the main reproductive organ of most of herbal plants but also an important part of Traditional Chinese Medicine (TCM). Seed TCMs possess important medicinal properties and have been widely used as components of pharmaceutical products. In parallel with the increasing popularity and accessibility of seeds as medicinal products in recent years, numerous substitutes and adulterants have also appeared on the market. Due to the small volume and similar appearances of many seed TCMs, they are very difficult to accurately identify the constituent plant species through organoleptic methods. Usage of the wrong herb may be ineffective or may worsen the condition and even cause death. Correct identification of seed herbal medicines is therefore essential for their safe use. Here, we acquired 177 ITS2 sequences and 15 psbA-trnH sequences from 51 kinds of seed TCMs belonging to 64 species that have been described in the Chinese Pharmacopoeia. Tree-building analysis showed that the ITS2 sequences of 48 seed TCMs can be differentiated from each other, and they formed distinct, non-overlapping groups in the maximum-likelihood tree. Furthermore, all of the sequences acquired in this study have been submitted to the public DNA barcoding system for herbal medicine, and this integrated database was used to identify 400 seed TCM samples purchased from medicinal markets, drug stores, and the Internet, enabling the identification of 7.5% of the samples as containing non-declared species. This study provides a brief operating procedure for the identification of seed TCMs found in herbal medicine. In the future, researchers and traditional herbal medicine enterprises can use this system to test their herbal materials

A Printed LPDA Antenna Fed by a Microstrip Line to Double Sided Parallel Strip Line from Backside

A novel planar printed log-periodic dipole array (LPDA) antenna fed by tapered microstrip line (MSL) to double sided parallel strip line (DSPSL) is proposed in this paper. The proposed antenna adopts MSL feeding approach from backside. Using this feeding technique makes the printed LPDA antenna easier to be integrated into radio frequency (RF) circuits. In this paper, four layers are used to construct the antenna. The four layers of the printed LPDA antenna are printed on three thin dielectric substrates which are integrated together. To validate this approach, a printed LPDA antenna is simulated and fabricated for operating in the S and C bands (2.5–6 GHz). The antenna showed a good result over the whole frequency range with 2 : 1 VSWR, an average gain of 6.5 dB, and stable radiation patterns. The measured results are in very good agreement with simulations

A novel DOA estimation algorithm for a 5-element circular array

Under the influence of the radome of the active and passive radar, the uniform circular array (UCA) becomes non-uniform in the electromagnetic performance, so the accuracy of direction of arrive (DOA) estimation is not high. This paper presents a universal look-up table algorithm for 5-element circular array to solve the problem. Firstly, we traverse the view field of the radar to obtain the long baseline phase differences of each angle point and store them to obtain the lookup table. Then, we can solve the incoming signal's long baseline phase differences on the array and compare them with the phase differences stored in the lookup table according to the maximum cosine value criterion. Finally, we can get the closest point and the corresponding angle is the angle of the incoming signal. Numerical simulation results and experimental results verify the effectiveness of the algorithm

Supplementary document for Optical Center of a Luminescent Solar Concentrator - 6030370.pdf

Supporting content

DOA estimation of LFM sources based on time-frequency interferometer in UCA

Based on the time-frequency (t-f) interferometer of the uniform circular array (UCA), a new direction of arrival (DOA) estimation algorithm of multiple linear frequency modulation (LFM) sources is proposed. Firstly, the cross smoothed pseudo Wigner-Ville distribution (SPWVD) of the elements’ output is calculated and the single source t-f points are selected by using a “noise threshold” procedure and cluster based algorithm. Then, by selecting different groups of sensor pairs, the proposed algorithm can solve the phase ambiguity of the t-f points by using a focusing based algorithm. And a lookup table based ambiguity resolution algorithm is also presented to reduce the computational complexity. The simulation results illustrate that the proposed t-f interferometer can be applied to multiple wideband LFM sources and it also can improve the DOA estimation precision compared with the traditional phase interferometer and sub-band interferometer. Especially in the low signal to noise ratio (SNR) and limited snapshots situations, the estimation root mean square errors (RMSEs) of the proposed algorithm are also within 3°

PSDSD-A Superpixel Generating Method Based on Pixel Saliency Difference and Spatial Distance for SAR Images

Superpixel methods are widely used in the processing of synthetic aperture radar (SAR) images. In recent years, a number of superpixel algorithms for SAR images have been proposed, and have achieved acceptable results despite the inherent speckle noise of SAR images. However, it is still difficult for existing algorithms to obtain satisfactory results in the inhomogeneous edge and texture areas. To overcome those problems, we propose a superpixel generating method based on pixel saliency difference and spatial distance for SAR images in this article. Firstly, a saliency map is calculated based on the Gaussian kernel function weighted local contrast measure, which can not only effectively suppress the speckle noise, but also enhance the fuzzy edges and regions with intensity inhomogeneity. Secondly, superpixels are generated by the local k-means clustering method based on the proposed distance measure, which can efficiently sort pixels to different clusters. In this step, the distance measure is calculated by combining the saliency difference and spatial distance with a proposed adaptive local compactness parameter. Thirdly, post-processing is utilized to clean up small segments. The evaluation experiments on the simulated SAR image demonstrate that our proposed method dramatically outperforms four state-of-the-art methods in terms of boundary recall, under-segmentation error, and achievable segmentation accuracy under almost all of the experimental parameters at a moderate segment speed. The experiments on real-world SAR images of different sceneries validate the superiority of our method. The superpixel results of the proposed method adhere well to the contour of targets, and correctly reflect the boundaries of texture details for the inhomogeneous regions