scholarly journals Extraction of Anisotropic Characteristics of Scattering Centers and Feature Enhancement in Wide-Angle SAR Imagery Based on the Iterative Re-Weighted Tikhonov Regularization

2018 ◽  
Vol 10 (12) ◽  
pp. 2066 ◽  
Author(s):  
Yuexin Gao ◽  
Mengdao Xing ◽  
Liang Guo ◽  
Zijing Zhang
Keyword(s):  
Tikhonov Regularization ◽  
High Efficiency ◽  
Anisotropic Scattering ◽  
Wide Angle ◽  
Scattering Center ◽  
Imaging Results ◽  
Scattering Centers ◽  
Novel Method ◽  
Sar Imagery ◽  
Actual Shape

The anisotropic characteristic reflects discriminating features of the geometry of a scattering center. In this study, we propose a novel method based on the iterative re-weighted Tikhonov regularization (IRWTR) to achieve the extraction of anisotropic characteristics of scattering centers in the wide-angle SAR synthetic aperture radar (SAR) imaging. Moreover, based on the extracted anisotropic scattering behaviors, the incomplete imaging results of the distributed scattering centers are restored. In this paper, we first discussed the scattering property in SAR imagery from the perspective of attributed scattering center model (ASCM). The reason for the incomplete imaging results of the distributed scattering centers was also discussed based on the ASCM. Subsequently, we modeled the aspect-dependent amplitude responses of a scattering center as a linear combination of a set of orthogonal basis. Consequently, the extraction of anisotropic characteristics can be transformed into an inverse problem, which was solved by the proposed IRWTR with high efficiency and accuracy. After the extraction, we attempted to restore the complete image of a distributed scattering center, which consisted of only two points. The enhanced SAR image can reveal the actual shape of a target. Processing results of electromagnetic computation data validated that the proposed method is effective and efficient.

scholarly journals Ultrawide-angle and high-efficiency metalens in hexagonal arrangement

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Chun-Yuan Fan ◽  
Chia-Ping Lin ◽  
Guo-Dung J. Su
Keyword(s):  
High Efficiency ◽  
Numerical Aperture ◽  
Vital Role ◽  
Optical Systems ◽  
Wide Field ◽  
Wide Angle ◽  
Camera Systems ◽  
Single Lens ◽  
Hexagonal Arrangement ◽  
Virtual And Augmented Reality

Abstract Wide-angle optical systems play a vital role in imaging applications and have been researched for many years. In traditional lenses, attaining a wide field of view (FOV) by using a single optical component is difficult because these lenses have crucial aberrations. In this study, we developed a wide-angle metalens with a numerical aperture of 0.25 that provided a diffraction-limited FOV of over 170° for a wavelength of 532 nm without the need for image stitching or multiple lenses. The designed wide-angle metalens is free of aberration and polarization, and its full width of half maximum is close to the diffraction limit at all angles. Moreover, the metalens which is designed through a hexagonal arrangement exhibits higher focusing efficiency at all angles than most-seen square arrangement. The focusing efficiencies are as high as 82% at a normal incident and 45% at an incident of 85°. Compared with traditional optical components, the proposed metalens exhibits higher FOV and provides a more satisfactory image quality because of aberration correction. Because of the advantages of the proposed metalens, which are difficult to achieve for a traditional single lens, it has the potential to be applied in camera systems and virtual and augmented reality.

Influence of Electron-Beam Annealing Duration on MgB2 Film Superconductivity

2013 ◽  
Vol 745-746 ◽  
pp. 255-260
Author(s):  
Xiang Dong Kong ◽  
Qian Dai ◽  
Han Li ◽  
Qing Rong Feng ◽  
Ming Zhang Chu ◽  
...  
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
High Efficiency ◽  
Beam Current ◽  
Annealing Duration ◽  
Zero Field ◽  
Superconducting Properties ◽  
Dense Structure ◽  
Novel Method ◽  
The Relationship

A novel method to fabricate Magnesium diboride ( MgB2) film by electron beam annealing was presented. The MgB2 thin films could be prepared in a second or sub-second without any toxic diborane gas, extra Mg vapor or argon gas. The method has the advantages of short formation time and high efficiency. Based on this, the relationship between MgB2 conductivity and electron beam annealing duration was investigated experimentally with an accelerating voltage of 40 × 103 V, a beam current of 3×103 A and different annealing durations of 0.1796s, 1860s, 0.2108s, 0.2200s and 0.2332s. The experimental results showed the MgB2 film with 0.2200s has the highest Tconset , the most dense structure and the strongest diamagnetic signal. Its zero-field Jc at 5 K was 5.0 × 106 A/cm2. Also the variation of the film superconducting properties with the annealing duration was found, it will provide an important reference for the preparation of high-quality MgB2 thin films.

scholarly journals The Synthesis of the Locating Substitution Derivatives of Chitosan by Click Reaction at the 6-Position of Chitin

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Yu Chen ◽  
Yanchun Ye ◽  
Yanyan Jing ◽  
YuanYuan Gao ◽  
Yanwen Guo ◽  
...  
Keyword(s):  
Nucleophilic Substitution ◽  
High Efficiency ◽  
Click Reaction ◽  
Macrocyclic Compound ◽  
Optimum Conditions ◽  
Structures And Properties ◽  
Acetyl Group ◽  
Novel Method ◽  
Derivatives Of

A novel method to prepare the macrocyclic compound locating substitution derivatives of chitosan was investigated, by using cyclodextrin as the model of macrocyclic compound. The method combines the advantages of activated 6-OH of chitin and high efficiency of click reaction. Chitin C6-OHp-toluenesulfonate (CTN-6-OTs) was generated and subsequently transferred to chitin C6-N3via nucleophilic substitution. Afterwards,β-cyclodextrin was immobilized at 6-OH of chitin via click reaction to afford CTN-6-CD. Ultimately, CTS-6-CD was obtained by removing the acetyl group of chitin unit. The structures and properties of these products were characterized by FTIR, TG, and XRD, respectively. It was found that CTN-6-CD synthesized at the optimum conditions has an immobilized loading of1.6126×10-4 mol/g and that of the corresponding CTS-6-CD, generated by removal of the acetyl group, was1.6891×10-4 mol/g.

scholarly journals Production of Gamma Alumina Using Plasma-Treated Aluminum and Water Reaction Byproducts

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1300 ◽  
Author(s):  
Marius Urbonavicius ◽  
Sarunas Varnagiris ◽  
Liudas Pranevicius ◽  
Darius Milcius
Keyword(s):  
High Purity ◽  
High Efficiency ◽  
Morphological Changes ◽  
Cost Effective ◽  
Electrical Energy ◽  
High Specific Surface Area ◽  
Direct Reaction ◽  
Gamma Alumina ◽  
Novel Method ◽  
High Purity Hydrogen

High purity hydrogen and solid-state byproducts are produced using a proposed plasma-activated aluminum and water reactions approach. These byproducts could be transformed into pure gamma Al2O3 powder material, while hydrogen can be used for electricity generation. Various chemical methods can be used for the synthesis of gamma alumina, but most could result in high levels of remaining impurities. Boehmite is a cost-effective starting material for the production of high-purity Al2O3. Herein, we present a novel method for the synthesis of boehmite and its transformation into high-specific-surface-area γ-alumina. Specifically, this method implicates the direct reaction between distilled water and plasma-treated aluminum powder. The results show the structural and morphological changes of the byproduct of the aluminum/water reaction to boehmite and γ-Al2O3 after a simple heating procedure (at 280 and 500 °C respectively). The high-purity hydrogen produced during the aluminum/water reaction can be used for the high-efficiency and environmentally friendly production of electrical energy.

Cortical Dipole Imaging of Movement-related Potentials by Means of Parametric Inverse Filters Incorporating with Signal and Noise Covariance

2007 ◽  
Vol 46 (02) ◽  
pp. 242-246 ◽  
Author(s):  
T. Miwa ◽  
T. Ohshima ◽  
B. He ◽  
J. Hori
Keyword(s):  
Tikhonov Regularization ◽  
Premotor Cortex ◽  
Dipole Source ◽  
Head Model ◽  
Spatial Filters ◽  
Source Imaging ◽  
Dipole Layer ◽  
Imaging Results ◽  
Related Potentials ◽  
Noise Covariance

Summary Objective : The objective of this study is to explore suitable spatial filters for inverse estimation of cortical equivalent dipole layer imaging from the scalp electroencephalogram. We utilize cortical dipole source imaging to locate the possible generators of scalpmeasured movement-related potentials (MRPs) in human. Methods : The effects of incorporating signal and noise covariance into inverse procedures were examined by computer simulations and experimental study. The parametric projection filter (PPF) and parametric Weiner filter (PWF) were applied to an inhomogeneous threesphere head model under various noise conditions. Results : The present simulation results suggest that the PWF incorporating signal information provides better cortical dipole layer imaging results than the PPF and Tikhonov regularization under the condition of moderate and high correlation between signal and noise distributions. On the other hand, the PPF has better performance than other inverse filters under the condition of low correlation between signal and noise distributions. The proposed methods were applied to self-paced MRPs in order to identify the anatomic substrate locations of neural generators. The dipole layer distributions estimated by means of PPF are well-localized as compared with blurred scalp potential maps and dipole layer distribution estimated by Tikhonov regularization. The proposed methods demonstrated that the contralateral premotor cortex was preponderantly activated in relation to movement performance. Conclusions : In cortical dipole source imaging, the PWF has better performance especiallywhen the correlation between the signal and noise is high. The proposed inverse method was applicable to human experiments of MRPs if the signal and noise covariances were obtained.

High efficiency fabrication of ultrahigh molecular weight polyethylene submicron filaments/sheets by flash-spinning

2016 ◽  
Vol 36 (1) ◽  
pp. 97-102 ◽  
Author(s):  
Lei Xia ◽  
Peng Xi ◽  
Bo-wen Cheng
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
High Efficiency ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Potential Method ◽  
Forming Process ◽  
Commercial Products ◽  
Ultrahigh Molecular Weight ◽  
Novel Method ◽  
Spinning Speed

Abstract In this study, we propose a novel method for preparing continuous ultrahigh molecular weight polyethylene (UHMWPE) filaments by flash-spinning. The filaments were processed by calendaring to obtain the sheets. The morphology of the filaments and the sheets, the forming process, the optimal fabrication conditions, mechanical properties, spinning speed, and the rate of spinning of the filaments were investigated. The results showed that the filaments were composed of bunches of microfibers and the diameter of the filaments and the microfibers ranged from 0.15 mm to 0.22 mm and 0.2 μm to 5 μm, respectively. For a given concentration of 5 wt% of the UHMWPE, optimal specimens were obtained only when the temperature was in the range 150–210°C and the pressure was in the range 8–20 MPa. The spinning speed and the polymer consumption increased with enhancement in the pressure and the value reached as high as 47.2 m/s and 116.7 g/min, respectively. The properties and the spinning efficiency of the filaments revealed that flash-spinning is a potential method for manufacturing commercial products in various fields of application.

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