Error bound of the multilevel adaptive cross approximation (MLACA)

An error bound of the multilevel adaptive cross approximation (MLACA 1, which is a multilevel version of the adaptive cross approximation-singular value decomposition (ACA-SVD), is rigorously derived. For compressing an off-diagonal submatrix of the method of moments MAD impedance matrix with a binary tree, the L-level MIACA includes L + 1 steps, and each step includes 2(L) ACA-SVD decompositions. If the relative Frobenius norm error of the ACA-SVD used in the MLACA is smaller than epsilon, the rigorous proof in this communication shows that the relative Frobenius norm error of the L-Ievel MLACA is smaller than (1 + epsilon)(L+1) - 1. In practical applications, the error bound of the MLACA can be approximated as epsilon(L + 1), because epsilon is always << 1. The error upper bound can he used to control the accuracy of the MLACA. To ensure an error of the L-level MLACA smaller than epsilon for different L, the ACA-SVD threshold can be set to (1 + epsilon)1/L+1 - 1, which approximately equals epsilon/(L + 1) for practical applications.Peer ReviewedPostprint (author's final draft

A Non-Invasive Interpretable NAFLD Diagnostic Method Combining TCM Tongue Features

Non-alcoholic fatty liver disease (NAFLD) is a clinicopathological syndrome characterized by hepatic steatosis resulting from the exclusion of alcohol and other identifiable liver-damaging factors. It has emerged as a leading cause of chronic liver disease worldwide. Currently, the conventional methods for NAFLD detection are expensive and not suitable for users to perform daily diagnostics. To address this issue, this study proposes a non-invasive and interpretable NAFLD diagnostic method, the required user-provided indicators are only Gender, Age, Height, Weight, Waist Circumference, Hip Circumference, and tongue image. This method involves merging patients' physiological indicators with tongue features, which are then input into a fusion network named SelectorNet. SelectorNet combines attention mechanisms with feature selection mechanisms, enabling it to autonomously learn the ability to select important features. The experimental results show that the proposed method achieves an accuracy of 77.22\% using only non-invasive data, and it also provides compelling interpretability matrices. This study contributes to the early diagnosis of NAFLD and the intelligent advancement of TCM tongue diagnosis. The project in this paper is available at: https://github.com/cshan-github/SelectorNet

TongueSAM: An Universal Tongue Segmentation Model Based on SAM with Zero-Shot

Tongue segmentation serves as the primary step in automated TCM tongue diagnosis, which plays a significant role in the diagnostic results. Currently, numerous deep learning based methods have achieved promising results. However, most of these methods exhibit mediocre performance on tongues different from the training set. To address this issue, this paper proposes a universal tongue segmentation model named TongueSAM based on SAM (Segment Anything Model). SAM is a large-scale pretrained interactive segmentation model known for its powerful zero-shot generalization capability. Applying SAM to tongue segmentation enables the segmentation of various types of tongue images with zero-shot. In this study, a Prompt Generator based on object detection is integrated into SAM to enable an end-to-end automated tongue segmentation method. Experiments demonstrate that TongueSAM achieves exceptional performance across various of tongue segmentation datasets, particularly under zero-shot. TongueSAM can be directly applied to other datasets without fine-tuning. As far as we know, this is the first application of large-scale pretrained model for tongue segmentation. The project and pretrained model of TongueSAM be publiced in :https://github.com/cshan-github/TongueSAM

Fast analysis and optimization of sparsely distributed partial modification problems

This article addresses the efficient numerical analysis of sparsely distributed small modifications in a large structure, that is, the sparsely distributed partial modification problem (SDPMP). A hierarchical matrix (H-matrix)-based fast direct solver is adopted to solve the SDPMP in a very short time for each new set of modifications. The main idea of this method is to reuse the parts of the compressed inverse matrix operator that do not change and only recompute the modified parts. In contrast with already existing algorithms designed to tackle a single localized modification, this new approach is still very fast for sparsely distributed small modifications, so it becomes a very attractive option to solve optimization problems efficiently, due to the very cheap analysis of the modified structure at each iteration of the optimization procedure. The efficiency of the solution of SDPMP is demonstrated for several cases involving passive and active metasurfaces and a reconfigurable antenna. As a practical example, a programmable metasurface reflector is optimized with particle swarm optimization to obtain a prescribed reflection pattern.This work was supported in part by the National Nature Science Foundation of China under Grant 61871219; in part by the China Scholarship Council under Grant 201906830042; in part by the Startup Foundation for Introducing Talent of the Nanjing University of Information Science and Technology (NUIST) under Grant 2022r079; in part by the Ministerio de Ciencia e Innovacion (MICINN) under Project PID2019- 107885GB-C31/AEI/10.13039/501100011033, Project PID2020-113832RBC21/AEI/10.13039/501100011033, and Project TEC2017-84817-C2-2-R/AEI/ 10.13039/501100011033; and in part by the Unidad de Excelencia Maria de Maeztu, which is financed by the Agencia Estatal de Investigación, Spain, under Grant MDM-2016-0600/AEI/10.13039/501100011033; and in part by the Catalan Agency for Management of University and Research Grants (AGAUR) under Research Group under Grant 2017 SGR 219.Peer ReviewedPostprint (author's final draft

A novel SWB antenna with triple band-notches based on elliptical slot and rectangular split ring resonators

In this paper, a wideband antenna was designed for super-wideband (SWB) applications. The proposed antenna was fed with a rectangular tapered microstrip feed line, which operated over a SWB frequency range (1.42 GHz to 50 GHz). The antenna was implemented at a compact size with electrical dimensions of 0.16 ¿ × 0.27 ¿ × 0.0047 ¿ mm3, where ¿ was with respect to the lowest resonance frequency. The proposed antenna prototype was fabricated on a F4B substrate, which had a permittivity of 2.65 and 1 mm thickness. The SWB antenna exhibited an impedance bandwidth of 189% and a bandwidth ratio of 35.2:1. Additionally, the proposed antenna design exhibited three band notch characteristics that were necessary to eradicate interference from WLAN, WiMAX, and X bands in the SWB range. One notch was achieved by etching an elliptical split ring resonator (ESRR) in the radiator and the other two notches were achieved by placing rectangular split ring resonators close to the signal line. The first notch was tuned by incorporating a varactor diode into the ESRR. The prototype was experimentally validated with, with notch and without notch characteristics for SWB applications. The experimental results showed good agreement with simulated results.Postprint (published version

Design of wideband beamforming metasurface with alternate absorption

In this paper, we propose a periodic structure that is capable of alternating between absorption and radiation mode. The designed periodic structure consists of an array of 6×6 square shaped unit cell. Each unit cell consists of a multi-layered structure, with dimensions of 0.5¿×0.5¿. The resonators are placed on the top layer and the feeding network is designed and implemented on the bottom layer. The ground layer is sandwiched between the two dielectric substrates. All resonators are connected to a 50 feed-line using the corporate feeding technique. To achieve broadband absorption, lumped resistors are inserted into the resonators. The proposed metasurface structure achieves broadband radiation, with low RCS and high gain, in the propagation direction whereas broadband absorption is achieved, when it is exposed to a free space plane wave. Moreover, the metamaterial absorber has stable absorptivity for an incident angle of (0¿–30¿). To verify the in-band absorption and radiation of the proposed design, a 6×6 periodic array of resonators has been fabricated and experimentally verified in an anechoic chamber. The measured results validate the performed simulations.Peer ReviewedPostprint (published version

Direction of Arrival Estimation Accuracy Enhancement via Using Displacement Invariance Technique

A new algorithm for improving Direction of Arrival Estimation (DOAE) accuracy has been carried out. Two contributions are introduced. First, Doppler frequency shift that resulted from the target movement is estimated using the displacement invariance technique (DIT). Second, the effect of Doppler frequency is modeled and incorporated into ESPRIT algorithm in order to increase the estimation accuracy. It is worth mentioning that the subspace approach has been employed into ESPRIT and DIT methods to reduce the computational complexity and the model’s nonlinearity effect. The DOAE accuracy has been verified by closed-form Cramér-Rao bound (CRB). The simulation results of the proposed algorithm are better than those of the previous estimation techniques leading to the estimator performance enhancement

A four‐way broadband filtering power divider with improved matching network for X‐band application

This study presents a novel design methodology of one-to-four filtering power divider (FPD) with a broadband response. It comprises three one-to-two power dividers (PDs) and a broadband bandpass filtering circuit in series. The impedance transformer of the one-to-two PD is designed into a dual-T-type symmetrical structure for improving the matching network and broadening the bandwidth, which includes a tapered transmission line, two cascaded microstrip lines with the same characteristic impedance, as well as a stepped-impedance open stub. The bandpass filtering circuit is formed by three coupled quarter-wavelength microstrip lines in parallel, where the intermediate subresonator is grounded via a hole instead of half wavelength line for pursuing a wider bandpass characteristic. The proposed FPD is fabricated and measured. The good performance is achieved with the return loss of >13.8 dB for input/output ports as well as minimum insertion loss of <0.21 dB (over the −6 dB splitting ratio) from 7.3 to 13 GHz.Nanyang Technological UniversityNational Research Foundation (NRF)This research work was conducted in the SMRT-NTU Smart Urban Rail Corporate Laboratory with funding support from the National Research Foundation (NRF), SMRT, and Nanyang Technological University, under the Corp Lab@University Scheme