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In this paper, we propose two parameter choice rules for the discretizing Tikhonov regularization via multiscale Galerkin projection for solving linear ill-posed integral equations. In contrast to previous theoretical analyses, we introduce a new concept called the projection noise level to obtain error estimates for the approximate solutions. This concept allows us to assess how noise levels change during projection. The balance principle and Hanke–Raus rule are modified by incorporating the error estimates of the projection noise level. We demonstrate the convergence rate of these two modified parameter choice rules through rigorous proof. In addition, we find that the error between the approximate solution and the exact solution improves as the noise frequency increases. Finally, numerical experiments are provided to illustrate the theoretical findings presented in this paper. [ABSTRACT FROM AUTHOR]

We propose a multilevel iteration method for the numerical solution of nonlinear ill-posed problems in the Hilbert space by using the Tikhonov regularization method. This leads to fast solutions of the discrete regularization methods for the nonlinear ill-posed equations. An adaptive choice of an a posteriori rule is suggested to choose the stopping index of iteration, and the rates of convergence are also derived. Numerical results are presented to demonstrate the efficiency and accuracy of the proposed method. [ABSTRACT FROM AUTHOR]

The increasing availability of multiplatform, multiband, very-high-resolution (VHR) satellite synthetic aperture radar (SAR) data has attracted the attention of a growing number of scientists and archeologists. In particular, over the last two decades, archeological research has benefited from SAR development mainly due to its unique ability to acquire scenes both at night and during the day under all weather conditions, its penetration capability, and the provided polarimetric and interferometric information. This paper explored the potential of a novel method (nonlocal (NL)-SAR) using TerraSAR-X (TSX) and Constellation of Small Satellites for Mediterranean Basin Observation (COSMO)-SkyMed (CSK) data to detect buried archeological remains in steep, rugged terrain. In this investigation, two test sites were selected in southern Tunisia, home to some of the most valuable and well-preserved limes from the Roman Empire. To enhance the subtle signals linked to archeological features, the speckle noise introduced into SAR data by the environment and SAR system must be mitigated. Accordingly, the NL-SAR method was applied to SAR data pertaining to these two significant test sites. Overall, the investigation (i) revealed a fortified settlement from the Roman Empire and (ii) identified an unknown urban area abandoned during this period via a field survey, thus successfully confirming the capability of SAR data to reveal unknown, concealed archeological sites, even in areas with a complex topography. [ABSTRACT FROM AUTHOR]

Commonly, a narrowband photodetector that can detect specific wavelengths is obtained by integrating a broadband photodetector with an external optical filter. However, this integration significantly increases the structural complexity and cost, and reduces the sensitivity. Herein, we demonstrate a filter-free, ultra-narrowband, ultraviolet photodetector based on a porous GaN/MoO3 heterojunction. Porous GaN with reduced defects and enhanced light trapping was fabricated by a facile photoelectrochemical etching method. The optimized porous GaN/MoO3 photodetector shows visible-blind (peaked at 370 nm) and ultra-narrowband (FWHM <10 nm) ultraviolet photoresponse. Moreover, the photodetector exhibits a large light-to-dark current ratio (nearly 105 at −3 V), along with a remarkable responsivity, external quantum efficiency, and detectivity of 187.5 mA W−1, 62.8%, and 4.34 × 1012 Jones, respectively. The highly-performing and narrowband response makes the porous GaN/MoO3 ultraviolet photodetector promising for secure optical communication systems. [ABSTRACT FROM AUTHOR]

With the launch of various multipolarimetric satellites, many scholars have introduced the persistent scatterer (PS)-oriented polarimetric optimization methods and extended the persistent scatterer interferometry (PSI) method to multipolarimetric data configuration, called polarimetric PSI (PolPSI) technology. Most PolPSI methods mainly take the amplitude dispersion index (ADI) as the optimization criterion and evaluate the temporal amplitude stationarity of each polarimetric channel for finding an optimal one. However, due to the unstable statistical characteristics of the quality indicator, many non-PS pixels are easily mistaken for the PS candidates (PSCs), and the performance of interferometric phase optimization is also limited. To overcome these restrictions, in this article, a novel PolPSI method is proposed based on the following two improved innovations. First, in terms of PSC selection, the trace moment (TM)-based statistical properties of time-series polarimetric coherency matrices are utilized for selecting the scatterers with the temporal polarimetric stationarity. Second, in terms of interferometric phase optimization, all interferometric coherency matrices of multipolarization channels are added up together to construct the total power (TP) interferogram for suppressing the effect of speckle noise and decorrelation. In the experiment, 13 scenes of quad-polarization ALOS PALSAR-1 image are selected to verify the algorithm’s effectiveness. The experimental results demonstrate that the proposed PolPSI method can better improve the deformation monitoring performance in three aspects than both the single-polarimetric HH and traditional exhaustive search polarimetric optimization (ESPO) methods, including phase quality improvement, density of PSs, and computational efficiency. [ABSTRACT FROM AUTHOR]

Core–shell heterojunction structure is a feasible approach to optimize the optoelectronic performance of devices by combining the advantages of different materials. In this work, GaN/AlN core–shell heterojunction microwire‐based photodetector (PD) has been fabricated, and appropriate epitaxy growth of AlN can improve the performances of PDs. Compared with pure GaN microwire device, the enhanced responsivity, sensitivity, detectivity, and external quantum efficiency value of 4160 A W−1, 1.88 × 107%, 3.93 × 1012 Jones, and 4.07 × 106% are obtained with 5 nm thick AlN. Meanwhile, a rise/decay time of 25/16 ms is possessed. In addition, the responsivity and detectivity are increased with an acceptable decrease in sensitivity when the exciting light intensity decreases. The effective advances of PDs are benefited from the increased Schottky barrier height, the built‐in electric field that promotes the separation of photogenerated electron‐hole pairs, and direct heteroepitaxial growth high crystal quality GaN/AlN core/shell structure, which will effectively passivate the surface of GaN microwire by covering AlN. This study sheds some light on fabricating high‐performance microwire‐based PDs. [ABSTRACT FROM AUTHOR]

Micro/nanowire light‐emitting diodes (LEDs) have inspired considerable research interests due to their potential applications in microdisplays and micro/nano‐optoelectronic integrated systems. Herein, a single InGaN/GaN multiple‐quantum‐well (MQW) microwire‐based flexible LED with high‐efficiency current injection and spreading is fabricated, and the performance modulation of the device by external strain is further studied. The results show that under external compressive strains, the output power is enhanced and the peak wavelength is blue shifted; on the contrary, the output power declines and the peak wavelength is red shifted under stretch strains. Compared with strain‐free devices, the flexible LED achieves the best performance at a − 1% compressive strain, with external quantum efficiency (EQE) increasing by 14.2% and efficiency droop reducing by 17.9%. The effective improvements are attributed to external strain‐induced piezoelectric polarization charges presented at local junctions/interfaces tuning the energy band. Herein, an efficient external modulation of light emission properties in a single InGaN/GaN MQW microwire LED is presented. [ABSTRACT FROM AUTHOR]

The traditional nonlocal estimations have been demonstrated to be effective and widely used in polarimetric synthetic aperture radar interferometry (PolInSAR) data. However, there still exist some problems about two key steps: 1) in the homogeneous pixels selection step, the regular square (RS) patches matching strategy shows the limited performance in textured area and 2) in the central pixel value estimation from the selected pixels, the well-known Lee estimator, which only uses the intensity statistic, tends to be unstable. To overcome these restrictions, we put forward two robust strategies and then propose an improved PolInSAR complex coherence nonlocal estimation: 1) the shape-adaptive (SA) patch is utilized for flexibly matching the similar pixels in a large search window, which is constructed by combining the likelihood ratio test (LRT) and the region growing (RG) algorithm and 2) the trace-moment-based nonlocal reduced bias (TMB-NLRB) estimator is employed, which considers the interchannel correlations and evaluates more accurately the homogeneity level between the selected pixels. The denoising effect of both strategies is quantitatively analyzed on the simulated data set, and the proposed algorithm is compared with classical estimation algorithms on a TerraSAR-X/TanDEM-X PolInSAR data set. These experimental results show that the proposed method provides better performance in speckle reduction, detail preservation, and complex coherence estimation. [ABSTRACT FROM AUTHOR]

The Daguangbao landslide was the largest landslide triggered by the "5.12" Wenchuan Mw 7.9 earthquake. This landslide is among the few superlarge‐scale landslides of 1 billion m3 magnitude worldwide. As the landslide accumulation represents a potential hazard, long‐term monitoring and geological interpretation of the Daguangbao landslide is important to reveal the postsliding deformation characteristics and laws of this landslide type. To study the kinematic characteristics 10 years postearthquake, the landslide accumulation deformation was monitored in two stages using different data sets and processing methods. First, regarding the deformation 2 years postearthquake, we selected PALSAR‐1 data (21 October 2008 to 14 March 2011) and obtained the LOS (line of sight) direction time series deformation of the landslide using the Small BAseline Subset (SBAS) algorithm. Second, for the last 4.5 years of deformation, Sentinel‐1 data sets (26 November 2015 to 8 June 2020) in two ascending and one descending path are experimentally used. The vertical and east‐west deformations during this period are obtained. Thickness, topography, precipitation, and other factors are combined to analyze the landslide accumulation deformation. The landslide accumulation volume decreases under gravitational influence, shrinkage is accelerated under precipitation influence, and periodic fluctuations occur, which lag precipitation changes. The maximum vertical direction deformation rate is below 80 mm/year, and the deformation magnitude in the east‐west direction is approximately ±35 mm/year. Local deformation is still affected by the surface slope and aspect, and the overall landslide accumulation movement trend involves gathering of the eastern and western parts toward the middle. In the observation window, with the stabilization of accumulation, the deformation tends decrease. Key Points: Analysis of the decadal kinematic characteristics of the landslide shows that landslide deformation tends to be decreasingThe overall landslide accumulation movement trend involves gathering of the eastern and western parts toward the middleThe landslide accumulation volume decreases under gravitational influence, and shrinkage is accelerated under precipitation influence [ABSTRACT FROM AUTHOR]

In this paper, we apply the multilevel augmentation method for solving ill-posed Fredholm integral equations of the first kind via iterated Tikhonov regularization method. The method leads to fast solutions of the discrete regularization methods for the equations. The convergence rates of iterated Tikhonov regularization are achieved by using a modified parameter choice strategy. Finally, numerical experiments are given to illustrate the efficiency of the method. [ABSTRACT FROM AUTHOR]

Triangular quantum barriers have been designed and investigated in this work to improve the performances of AlGaN-based ultraviolet light-emitting diodes (UV-LEDs). The results show that the designed LED with triangular quantum barriers has been enhanced by 63.6% in light output power, while the efficiency droop has been reduced to 14.8% at an injection current of 180 mA, compared with the conventional LED with a stationary component Al0.15Ga0.85N barriers. Further research shows that the improvements of the proposed structure are due to the enhanced hole injection efficiency and the suppressed electron overflow as well as the decreased electrostatic field in the active region. [ABSTRACT FROM AUTHOR]

In this paper we apply the multilevel augmentation method to solve an ill-posed integral equation via the iterated Lavrentiev regularization. This method leads to fast solutions of discrete iterated Lavrentiev regularization. The convergence rates of the iterated Lavrentiev regularization are achieved by using a certain parameter choice strategy. Finally, numerical experiments are given to illustrate the efficiency of the method. [ABSTRACT FROM AUTHOR]

Considering their reduced size and weight, low cost and portability, self-powered photodetectors that can be functioned independently of an external power supply are extremely important for developing future sensor networks and Internets of Things. Here, we present a self-powered photodetector with a broadband wavelength photoresponse from the ultraviolet to near-infrared region based on GaN microwire array/Si heterojunctions. Due to the highly efficient separation of photogenerated charge carriers, the photodetector shows ultrahigh EQE, responsivity and detectivity, reaching up to 71%, 4.7 × 102 mA W−1 and 9.5 × 1012 Jones, respectively, at zero bias in the 320–850 nm range. A fast response is observed with rise/decay times as low as 2/2 ms. The LDR values are over 80 dB. The performance characteristics are competitive with commercially available biased photodetectors and other reported heterojunction self-powered broadband photodetectors in the literature. In addition, a binary photoresponse is observed under small bias voltages. The heterostructures are fabricated by directly heteroepitaxially growing GaN microwires on patterned Si, enabling large-area device applications, and stand out from low-dimensional semiconductor photodetection systems. The overall high performance coupled with large-scale production makes GaN microwire array/Si heterojunctions promising for practical self-powered broadband photodetectors. [ABSTRACT FROM AUTHOR]

In this paper, multilevel Jacobi and Gauss-Seidel type iteration methods with compression technique are developed for solving ill-posed integral equations by making use of the multiscale structure of the matrix representation of the integral operator. The methods are based on the combination of Tikhonov regularization and multiscale Galerkin methods, and lead to fast solutions of discrete regularization methods for the equations. Choice for an a posteriori regularization parameter is proposed. An optimal convergence order for the method with the choices of parameters is established. Numerical experiments are given to illustrate the efficiency of the method. [ABSTRACT FROM AUTHOR]

Abstract: We develop a multilevel iteration method with compression technique for solving ill-posed integral equations. The method leads to fast solutions of discrete regularization methods for the equations. Choice for a posteriori regularization parameter is proposed. An optimal convergence order for the method with the choices of parameters is established. The theoretical analysis and numerical experiments illustrate the accuracy and efficiency of the algorithm. [Copyright &y& Elsevier]

In this paper we develop a fast multiscale Galerkin method solving ill-posed integral equations with not exactly given input data via Tikhonov regularization. The method leads to fast solutions of discrete Tikhonov regularization. The convergence rates of the Tikhonov regularization are achieved by using a modified discrepancy principle. Finally, numerical experiments are given to illustrate the efficiency of the method. [ABSTRACT FROM AUTHOR]

A piezoelectric ultrasonic transducer (PUT) is widely used in nondestructive testing, medical imaging, and particle manipulation, etc., and the performance of the PUT determines its functional performance and effectiveness in these applications. The optimization design method of a PUT is very important for the fabrication of a high-performance PUT. In this paper, traditional and efficient optimization design methods for a PUT are presented. The traditional optimization design methods are mainly based on an analytical model, an equivalent circuit model, or a finite element model and the design parameters are adjusted by a trial-and-error method, which relies on the experience of experts and has a relatively low efficiency. Recently, by combining intelligent optimization algorithms, efficient optimization design methods for a PUT have been developed based on a traditional model or a data-driven model, which can effectively improve the design efficiency of a PUT and reduce its development cycle and cost. The advantages and disadvantages of the presented methods are compared and discussed. Finally, the optimization design methods for PUT are concluded, and their future perspectives are discussed. [ABSTRACT FROM AUTHOR]

In the traditional single polarimetric persistent scatterers interferometric (PSI) technology, the amplitude dispersion index (ADI) is usually used to select persistent scatterer candidates (PSC). Obviously, based on single polarimetric information, it is difficult to use the statistical characteristics for comprehensively describing the temporal stability of scatterers, which leads to a decrease in persistent scatterer (PS) density. Considering that the temporal polarimetric stationarity of PS, the paper is based on complex Wishart distribution and proposes the polarimetric stationarity omnibus test (PSOT) for identifying PSC. The nonstationary pixels can be removed by the preset significance threshold, which reduces the subsequent processing error and the calculation cost. Then, the exhaustive search polarimetric optimization (ESPO) method is selected for improving the phase quality of PSCs while suppressing the sidelobe of the strong scatterer effectively. For validating the effectiveness of the proposed method, we select a time-series quad-polarimetric ALOS PALSAR-1 images in an urban area as experimental data and mainly perform five group experiments for detailed analysis, including the PSOT+ESPO, ADI+ESPO, ADI+HH, ADI+HV, and ADI+VV. The results show that the proposed PSOT+ESPO method has a better performance on both PSC selection and interferometric phase optimization aspects than that of other methods. Specifically, compared to the last four methods, both the PSCs and PSs identified by the proposed PSOT+ESPO are more concentrated in the high-coherence region. The PSs with the standard deviation (STD) less than 5mm in the PSOT+ESPO method account for 94% of all PSs, which is greater than that of the ADI+ESPO, ADI+HH, ADI+HV, and ADI+VV methods, respectively. [ABSTRACT FROM AUTHOR]

In this paper, Landweber iteration with a relaxation factor is proposed to solve nonlinear ill-posed integral equations. A compression multiscale Galerkin method that retains the properties of the Landweber iteration is used to discretize the Landweber iteration. This method leads to the optimal convergence rates under certain conditions. As a consequence, we propose a multiscale compression algorithm to solve nonlinear ill-posed integral equations. Finally, the theoretical analysis is verified by numerical results. [ABSTRACT FROM AUTHOR]

As ideal building blocks for optoelectronic devices, one-dimensional (1D) single-crystal perovskite microwires (MWs) have received widespread attention due to their unique physical and chemical properties. Herein, a one-step solution in-plane self-assembly method is proposed to directly grow millimeter-long CsPbBr 3 MWs with superior crystal quality at atmospheric environment. This method effectively avoids the use of toxic antisolvents. Furthermore, a MW-based photodetector is successfully fabricated, showing high photoresponsivity (20 A/W) and fast response (less than 0.3 ms). The stability of the photodetector is also confirmed by aging MW in air for 60 days, which shows a negligible change of photocurrent from 1.29 to 1.25 nA (-3 V) under the same experimental conditions. This work provides a low-cost and fast synthesis method for the preparation of single-crystal perovskite MWs and demonstrates their potential application for high-performance and stable photoelectronic device.

The high mortality associated with conventionally resuscitated septic shock and the subsequent multiple-organ failure remain a very significant and costly clinical problem. Conventional simple intravenous resuscitation (CR) from septic shock often fails to restore the progressive splanchnic vasoconstriction and hypoperfusion, and fails to reverse gut-derived systemic inflammatory response and fluid sequestration. Numerous interventions have been used to protect organ systems and cellular viability from the lethal injury accompanying hypoperfusion and ischemia but none of these efforts have been sufficient to halt or reverse the main course of the pathophysiology noted with conventional resuscitated shock. Recently, some studies have found that in hemorrhagic shock, direct peritoneal resuscitation (DPR) not only produces sustained hyperperfusion in viscera but also has immunomodulatory and anti-fluid sequestration effects. Although the etiology and pathogenesis of septic shock and hemorrhagic shock differ, both kinds of shock result in hypoperfusion of the intestines and other internal organs. In this paper, we seek to determine whether DPR has a similar therapeutic effect on septic shock/resuscitation.