Symmetry Pub Date : 2024-09-18 DOI: 10.3390/sym16091223

Emerson Raja Joseph, Hossen Jakir, Bhuvaneswari Thangavel, Azlina Nor, Thong Leng Lim, Pushpa Rani Mariathangam

{"title":"Tool-Emitted Sound Signal Decomposition Using Wavelet and Empirical Mode Decomposition Techniques—A Comparison","authors":"Emerson Raja Joseph, Hossen Jakir, Bhuvaneswari Thangavel, Azlina Nor, Thong Leng Lim, Pushpa Rani Mariathangam","doi":"10.3390/sym16091223","DOIUrl":"https://doi.org/10.3390/sym16091223","url":null,"abstract":"Analysis of non-stationary and nonlinear sound signals obtained from dynamical processes is one of the greatest challenges in signal processing. Turning machine operation is a highly dynamic process influenced by many events, such as dynamical responses, chip formations and the operational conditions of machining. Traditional and widely used fast Fourier transformation and spectrogram are not suitable for processing sound signals acquired from dynamical systems as their results have significant deficiencies because of stationary assumptions and having an a priori basis. A relatively new technique, discrete wavelet transform (DWT), which uses Wavelet decomposition (WD), and the recently developed technique, Hilbert–Huang Transform (HHT), which uses empirical mode decomposition (EMD), have notably better properties in the analysis of nonlinear and non-stationary sound signals. The EMD process helps the HHT to locate the signal’s instantaneous frequencies by forming symmetrical envelopes on the signal. The objective of this paper is to present a comparative study on the decomposition of multi-component sound signals using EMD and WD to highlight the suitability of HHT to analyze tool-emitted sound signals received from turning processes. The methodology used to achieve the objective is recording a tool-emitted sound signal by way of conducting an experiment on a turning machine and comparing the results of decomposing the signal by WD and EMD techniques. Apart from the short mathematical and theoretical foundations of the transformations, this paper demonstrates their decomposition strength using an experimental case study of tool flank wear monitoring in turning. It also concludes HHT is more suitable than DWT to analyze tool-emitted sound signals received from turning processes.","PeriodicalId":501198,"journal":{"name":"Symmetry","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A Channel-Sensing-Based Multipath Multihop Cooperative Transmission Mechanism for UE Aggregation in Asymmetric IoE Scenarios 一种基于信道传感的多路径多跳合作传输机制，用于非对称物联网场景中的 UE 聚合

Symmetry Pub Date : 2024-09-18 DOI: 10.3390/sym16091225

Hua-Min Chen, Ruijie Fang, Shoufeng Wang, Zhuwei Wang, Yanhua Sun, Yu Zheng

{"title":"A Channel-Sensing-Based Multipath Multihop Cooperative Transmission Mechanism for UE Aggregation in Asymmetric IoE Scenarios","authors":"Hua-Min Chen, Ruijie Fang, Shoufeng Wang, Zhuwei Wang, Yanhua Sun, Yu Zheng","doi":"10.3390/sym16091225","DOIUrl":"https://doi.org/10.3390/sym16091225","url":null,"abstract":"With the continuous progress and development of technology, the Internet of Everything (IoE) is gradually becoming a research hotspot. More companies and research institutes are focusing on the connectivity and transmission between multiple devices in asymmetric networks, such as V2X, Industrial Internet of Things (IIoT), environmental monitoring, disaster management, agriculture, and so on. The number of devices and business volume of these applications have rapidly increased in recent years, which will lead to a large load of terminals and affect the transmission efficiency of IoE data transmission. To deal with this issue, it has been proposed to perform data transmission via multipath cooperative transmission with multihop transmission. This approach aims to improve transmission latency, energy consumption, reliability, and throughput. This paper designs a channel-sensing-based cooperative transmission mechanism (CSCTM) with hybrid automatic repeat request (HARQ) for user equipment (UE) aggregation mechanism in future asymmetric IoE scenarios, which ensures that IoE devices data can be transmitted quickly and reliably, and supports real-time data processing and analysis. The main contents of this proposed method include strategies of cooperative transmission and redundancy version (RV) determination, a joint combination of decoding process at the receiving side, and a design of transmission priority through ascending offset sort (AOS) algorithm based on channel sensing. In addition, multihop technology is designed for the multipath cooperative transmission strategy, which enables cooperative nodes (CN) to help UE to transmit data. As a result, it can be obtained that CSCTM provides significant advancements in latency and energy consumption for the whole system. It demonstrates improvements in enhanced coverage, improved reliability, and minimized latency.","PeriodicalId":501198,"journal":{"name":"Symmetry","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261441","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Three-Dimensional Moran Walk with Resets 带重置的三维莫兰步

Symmetry Pub Date : 2024-09-18 DOI: 10.3390/sym16091222

Mohamed Abdelkader

引用次数: 0

Balance Controller Design for Inverted Pendulum Considering Detail Reward Function and Two-Phase Learning Protocol 考虑详细奖励函数和两阶段学习协议的倒立摆平衡控制器设计

Symmetry Pub Date : 2024-09-18 DOI: 10.3390/sym16091227

Xiaochen Liu, Sipeng Wang, Xingxing Li, Ze Cui

{"title":"Balance Controller Design for Inverted Pendulum Considering Detail Reward Function and Two-Phase Learning Protocol","authors":"Xiaochen Liu, Sipeng Wang, Xingxing Li, Ze Cui","doi":"10.3390/sym16091227","DOIUrl":"https://doi.org/10.3390/sym16091227","url":null,"abstract":"As a complex nonlinear system, the inverted pendulum (IP) system has the characteristics of asymmetry and instability. In this paper, the IP system is controlled by a learned deep neural network (DNN) that directly maps the system states to control commands in an end-to-end style. On the basis of deep reinforcement learning (DRL), the detail reward function (DRF) is designed to guide the DNN learning control strategy, which greatly enhances the pertinence and flexibility of the control. Moreover, a two-phase learning protocol (offline learning phase and online learning phase) is proposed to solve the “real gap” problem of the IP system. Firstly, the DNN learns the offline control strategy based on a simplified IP dynamic model and DRF. Then, a security controller is designed and used on the IP platform to optimize the DNN online. The experimental results demonstrate that the DNN has good robustness to model errors after secondary learning on the platform. When the length of the pendulum is reduced by 25% or increased by 25%, the steady-state error of the pendulum angle is less than 0.05 rad. The error is within the allowable range. The DNN is robust to changes in the length of the pendulum. The DRF and the two-phase learning protocol improve the adaptability of the controller to the complex and variable characteristics of the real platform and provide reference for other learning-based robot control problems.","PeriodicalId":501198,"journal":{"name":"Symmetry","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Magnetohydrodynamic Waves in Asymmetric Waveguides and Their Applications in Solar Physics—A Review 不对称波导中的磁流体动力波及其在太阳物理学中的应用--综述

Symmetry Pub Date : 2024-09-18 DOI: 10.3390/sym16091228

Robertus Erdélyi, Noémi Kinga Zsámberger

{"title":"Magnetohydrodynamic Waves in Asymmetric Waveguides and Their Applications in Solar Physics—A Review","authors":"Robertus Erdélyi, Noémi Kinga Zsámberger","doi":"10.3390/sym16091228","DOIUrl":"https://doi.org/10.3390/sym16091228","url":null,"abstract":"The solar atmosphere is a complex, coupled, highly dynamic plasma environment, which shows rich structuring due to the presence of gravitational and magnetic fields. Several features of the Sun’s atmosphere can serve as guiding media for magnetohydrodynamic (MHD) waves. At the same time, these waveguides may contain flows of various magnitudes, which can then destabilise the waveguides themselves. MHD waves were found to be ubiquitously present in the solar atmosphere, thanks to the continuous improvement in the spatial, temporal, and spectral resolution of both space-born and ground-based observatories. These detections, coupled with recent theoretical advancements, have been used to obtain diagnostic information about the solar plasma and the magnetic fields that permeate it, by applying the powerful concept of solar magneto-seismology (SMS). The inclusion of asymmetric shear flows in the MHD waveguide models used may considerably affect the seismological results obtained. Further, they also influence the threshold for the onset of the Kelvin–Helmholtz instability, which, at high enough relative flow speeds, can lead to energy dissipation and contribute to the heating of the solar atmosphere—one of the long-standing and most intensely studied questions in solar physics.","PeriodicalId":501198,"journal":{"name":"Symmetry","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Optimization of Aviation Technologies and Design Strategies for a Carbon-Neutral Future 优化航空技术和设计战略，实现碳中和的未来

Symmetry Pub Date : 2024-09-18 DOI: 10.3390/sym16091226

Zheng Xu, Jinze Pei, Yue Song

引用次数: 0

A New Multimodal Modification of the Skew Family of Distributions: Properties and Applications to Medical and Environmental Data Skew 分布家族的一种新的多模式修正：特性及在医疗和环境数据中的应用

Symmetry Pub Date : 2024-09-18 DOI: 10.3390/sym16091224

Jimmy Reyes, Mario A. Rojas, Pedro L. Cortés, Jaime Arrué

{"title":"A New Multimodal Modification of the Skew Family of Distributions: Properties and Applications to Medical and Environmental Data","authors":"Jimmy Reyes, Mario A. Rojas, Pedro L. Cortés, Jaime Arrué","doi":"10.3390/sym16091224","DOIUrl":"https://doi.org/10.3390/sym16091224","url":null,"abstract":"The skew distribution has the characteristic of appropriately modeling asymmetric unimodal data. However, in practice, there are several cases in which the data present more than one mode. In the literature, it is possible to find a large number of authors who have studied extensions based on the skew distribution to model this type of data. In this article, a new family is introduced, consisting of a multimodal modification to the family of skew distributions. Using the methodology of the weighted version of a function, we perform the product of the density function of a family of skew distributions with a polynomial of degree 4, thus obtaining a more flexible model that allows modeling data sets, whose distribution contains at most three modes. The density function, some properties, moments, skewness coefficients, and kurtosis of this new family are presented. This study focuses on the particular cases of skew-normal and Laplace distributions, although it can be applied to any other distribution. A simulation study was carried out, to study the behavior of the model parameter estimates. Illustrations with real data, referring to medicine and environmental data, show the practical performance of the proposed model in the two particular cases presented.","PeriodicalId":501198,"journal":{"name":"Symmetry","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261442","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study of Behavior of Geometric Symmetries of 3D Objects with Digital Fresnel–Kirchhoff Holograms, Using Non-Redundant Calculations 利用非冗余计算研究数字菲涅尔-基尔霍夫全息图的三维物体几何对称性行为

Symmetry Pub Date : 2024-09-17 DOI: 10.3390/sym16091219

Joan Manuel Villa-Hernández, Arturo Olivares-Pérez, Roxana Herran-Cuspinera, José Luis Juárez-Pérez, Luis Mancio, Rocío Delesma

{"title":"Study of Behavior of Geometric Symmetries of 3D Objects with Digital Fresnel–Kirchhoff Holograms, Using Non-Redundant Calculations","authors":"Joan Manuel Villa-Hernández, Arturo Olivares-Pérez, Roxana Herran-Cuspinera, José Luis Juárez-Pérez, Luis Mancio, Rocío Delesma","doi":"10.3390/sym16091219","DOIUrl":"https://doi.org/10.3390/sym16091219","url":null,"abstract":"Techniques for producing fast Huygens–Fresnel–Kirchhoff digital holograms using kernel symmetry are studied. This study demonstrates non-linear behavior in computing time, as the sampled area changes with respect to the propagated diffracted area. Given the large amount of data involved in 3D object formation, symmetries are crucial in reducing the computational time. The evaluation of diffraction patterns is implemented to avoid redundant calculations while preserving the precision of the results. This algorithm decreases the required computing time depending on the symmetry of the axes, compared to direct calculation. Interestingly, the reduction in computing time relative to the number of symmetries is not linear. Computing time curves are presented. Some redundant computations are determined by the initial conditions of the object matrix, whether even or odd, along its x and y axes. Diagonal symmetries possess intrinsic redundancy along their axes. The rotation of the image must align with the rotation of the geometric coordinates in each section to ensure accurate calculations.","PeriodicalId":501198,"journal":{"name":"Symmetry","volume":"194 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261462","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Concomitant Observer-Based Multi-Level Fault-Tolerant Control for Near-Space Vehicles with New Type Dissimilar Redundant Actuation System 基于观测器的近空间飞行器多级容错协同控制与新型异构冗余执行系统

Symmetry Pub Date : 2024-09-17 DOI: 10.3390/sym16091221

Meiling Wang, Jun Wang, Jian Huang

{"title":"Concomitant Observer-Based Multi-Level Fault-Tolerant Control for Near-Space Vehicles with New Type Dissimilar Redundant Actuation System","authors":"Meiling Wang, Jun Wang, Jian Huang","doi":"10.3390/sym16091221","DOIUrl":"https://doi.org/10.3390/sym16091221","url":null,"abstract":"This paper presents a concomitant observer-based multi-level fault-tolerant control (FTC) for near-space vehicles (NSVs) with a new type dissimilar redundant actuation system (NT-DRAS). When NSV flight control system faults occur in NT-DRAS and attitude-corresponding sensors, the NSV hybrid output states, including the concomitant observer usable states and the real system states, are applied to solve the FTC gain by using the linear quadratic regulator (LQR) technique. Furthermore, since NT-DRAS is used in NSVs, a multi-level (actuation system level and flight control level) FTC strategy integrating NT-DRAS channel switching and flight control LQR is proposed for complex and worsening fault cases. The most important finding is that though the proposed strategy is applicable for worsening fault cases in NSVs, systematic and accurate criteria for the process being performed are necessary and can improve the FTC efficiency with minimal FTC resources. Additionally, such criteria can improve the NSV’s responsiveness to comprehensive faults, provided that the real-time performance of the fault detection and diagnosis (FDD) scheme can be further optimized. The concomitant observer convergence and the multi-level FTC strategy have been verified by numerical simulations based on the Matlab/Simulink platform.","PeriodicalId":501198,"journal":{"name":"Symmetry","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142261465","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Experiments of Ultrasonic Positioning System with Symmetrical Array Used in Jiangmen Underground Neutrino Observatory 江门地下中微子观测站使用的对称阵列超声波定位系统实验

Symmetry Pub Date : 2024-09-17 DOI: 10.3390/sym16091218

Guolei Zhu, Wenxin Yang, Duo Teng, Qi Wang, Jiaqi Hui, Jie Lian

引用次数: 0

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