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A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Computer".

Deadline for manuscript submissions: closed (30 June 2022) | Viewed by 22813

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Dr. Raúl Baños Navarro

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Guest Editor

Department of Engineering, Electrical Engineering section, University of Almería, E-04120 Almería, Spain
Interests: energy economics; renewable energy; power meters; network analysis; engineering optimization
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Francisco G. Montoya

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Guest Editor

Department of Engineering, Electrical Engineering Section, University of Almeria, 04120 Almeria, Spain
Interests: geometric algebra; power quality; power theory; power engineering; optimization techniques
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Symmetry is a frequent pattern widely studied in different research fields. In particular, complex systems with symmetric and asymmetric characteristics arise in engineering science (e.g., in mechanical engineering, symmetric and synchronized systems are often used to satisfy stability criteria for rotating structures; in electrical engineering, the study of symmetrical and asymmetrical faults in power systems is a critical issue; in telecommunications engineering, many systems are symmetrical since data speed or quantity is the same in both directions; in civil engineering, the strength of the objects depends on the symmetry; in computer engineering, symmetric network structures and symmetric algorithms are often studied; etc.).

This Special Issue invites researchers to submit original research papers and review articles related to any engineering discipline in which theoretical or practical issues of symmetry are considered. The topics of interest include (but are not limited to):

Symmetry in electrical engineering (power, electronics, electromechanics, computer, control, microwaves, telecommunications, etc.);
Symmetry in mechanical engineering (acoustical, aerospace, automotive, marine, railway, thermal, etc.);
Symmetry in civil engineering (architectural, construction, earthquake, environmental, hydraulic, mining, structural, transportation, etc.);
Symmetry in chemical engineering (biochemical, molecular, processes, thermodynamics, etc.);
Symmetry in other interdisciplinary engineering disciplines (agricultural, biomedical, graphical modelling, industrial, information, materials, metallurgy, military, nanotechnology, control, automation, robotics, etc.);
Symmetry and topology of complex networks in engineering;
Symmetry and optimization in engineering applications.

Prof. Raúl Baños
Prof. Dr. Francisco G. Montoya
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Symmetry is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

Symmetry and asymmetry
Symmetry and synchronization
Symmetry operations
Symmetry measures
Topological symmetry
Geometric symmetry
Symmetry in complex systems
Complex networks and graphs
Optimization
Computation
Electrical engineering
Mechanical engineering
Civil engineering
Chemical engineering

Published Papers (9 papers)

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Research

18 pages, 3096 KiB

Open AccessArticle

A New Approach to the Embedding of Delamination in the Layerwise Theory of Laminated Composite Plates

by Marina Rakočević and Ljiljana Žugić

Symmetry 2022, 14(8), 1583; https://doi.org/10.3390/sym14081583 - 01 Aug 2022

Cited by 1 | Viewed by 1136

Abstract

This paper presents a new analytical approach to the embedding of delamination in the layerwise theory, which can be applied to determine the stress–strain state in the cross-section of laminated plates with internal delamination. The new approach is based on the layerwise theory, which transfers considerations from the level of the laminated plate to the level of the lamina. The paper presents a mathematical model and defines a calculation procedure for determining the state of the stress and strain in a cross-section with an internal delamination that occurred during plate production. The convergence and stability of the computational procedure, based on a new approach to the embedding of delamination in layerwise theory, are proven. It is also proven that the existence of internal delamination on the bond between layers of laminated plates significantly changes the stress-strain state of the cross-section, in relation to a cross-section without delamination. In numerical examples, the value of delamination in the plane (x, y) is determined and considered. The initial state after a static load or “zero state” of stress and strain in a cross-section with delamination represent the input for further and future nonlinear analyses that involve the growth, development, and propagation of delamination. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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15 pages, 5293 KiB

Open AccessArticle

Vibration Measurement Using Laser Triangulation for Applications in Wind Turbine Blades

by Víctor Iván Moreno-Oliva, Ociel Flores-Diaz, Edwin Román-Hernández, Manuel Campos-García, Eduardo Campos-Mercado, José Rafael Dorrego-Portela, Quetzalcoatl Hernandez-Escobedo, Jesus Alejandro Franco, Alberto-Jesus Perea-Moreno and Alfredo Alcayde García

Symmetry 2021, 13(6), 1017; https://doi.org/10.3390/sym13061017 - 06 Jun 2021

Cited by 6 | Viewed by 3233

Abstract

The blades in a wind turbine are currently manufactured with flexible and light materials, which make them more susceptible to the effects of vibrations when the wind speed is high enough, causing fatigue damage, affecting the functionality of its structure and aerodynamic efficiency. This work presents a comparison of the modal vibration parameters, applied to a cantilever beam, determined with two experimental methods—the use of accelerometers and a proposed optical non-contact method—based on the principle of laser triangulation and photogrammetry techniques. This technique uses the geometric symmetry of the equidistant displacements along the z axis of the beam to obtain the amplitude data. Parameters such as natural frequency and modal form are obtained by fitting the data to a nonlinear equation with a solution which is an exponential/harmonic equation. Also, analytically, these parameters are determined, and a comparison is made between the experimental methods. The result shows that the relative error of the first-order natural vibration frequency is below 1%. The proposed method is simple, efficient, reliable, and it is also a method that has not been applied to the test of wind turbine blades, so its implementation as this type of wind turbine component is an area of opportunity for the validation of modal vibration parameters in the wind industry. An analysis of results is presented showing benefits of the proposed method and its limitations. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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15 pages, 1027 KiB

Open AccessArticle

A Generalization of the Importance of Vertices for an Undirected Weighted Graph

by Ronald Manríquez, Camilo Guerrero-Nancuante, Felipe Martínez and Carla Taramasco

Symmetry 2021, 13(5), 902; https://doi.org/10.3390/sym13050902 - 19 May 2021

Cited by 6 | Viewed by 2419

Abstract

Establishing a node importance ranking is a problem that has attracted the attention of many researchers in recent decades. For unweighted networks where the edges do not have any attached weight, many proposals have been presented, considering local or global information of the networks. On the contrary, it occurs in undirected edge-weighted networks, where the proposals to address this problem have been more scarce. In this paper, a ranking method of node importance for undirected and edge-weighted is provided, generalizing the measure of line importance (DIL) based on the centrality degree proposed by Opsahl. The experimentation was done on five real networks and the results illustrate the benefits of our proposal. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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21 pages, 17818 KiB

Open AccessArticle

Effectiveness Assessment of CAD Simulation in Complex Orthopedic Surgery Practices

by Leonardo Frizziero, Curzio Pagliari, Giampiero Donnici, Alfredo Liverani, Gian Maria Santi, Paola Papaleo, Francesca Napolitano, Christian Leon-Cardenas, Giovanni Trisolino, Paola Zarantonello, Giovanni Luigi Di Gennaro, Stefano Stilli and Stefano Stallone

Symmetry 2021, 13(5), 850; https://doi.org/10.3390/sym13050850 - 11 May 2021

Cited by 2 | Viewed by 2294

Abstract

This experimental study defines the usage of a computer-aided surgical simulation process that is effective, safe, user-friendly, and low-cost, that achieves a detailed and realistic representation of the anatomical region of interest. The chosen tools for this purpose are state-of-the-art Computer Aided Design (CAD) software for mechanical design, and are the fundamental application dedicated to parametric modeling. These tools support different work environments, each one is for a specific type of modeling, and they allow the simulation of surgery. The result will be a faithful representation of the anatomical part both before and after the surgical procedure, screening all the intermediate phases. The doctor will assess different lines of action according to the results, then he will communicate them to the engineer who, consequently, will correct the antisymmetric issue and regenerate the model. Exact measurements of the mutual positions of the various components, skeletal and synthetic, can be achieved; all the osteosynthesis tools, necessary for the surgeon, can be included in the project according to different types of fracture to perfectly match the morphology of the bone to be treated. The method has been tested on seven clinical cases of different complexity and nature and the results of the simulations have been found to be of great effectiveness in the phase of diagnosis and of preoperative planning for the doctors and surgeons; therefore, allowing a lower risk medical operation with a better outcome. This work delivers experimental results in line with theoretical research findings in detail; moreover, full experimental and/or methodical details are provided, so that outcomes could be obtained. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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17 pages, 3198 KiB

Open AccessArticle

Sensitivity Analysis of Rigid Pavement Design Based on Semi-Empirical Methods: Romanian Case Study

by Costel Pleșcan, Elena-Loredana Pleșcan, Mariana D. Stanciu, Marius Botiș and Daniel Taus

Symmetry 2021, 13(2), 168; https://doi.org/10.3390/sym13020168 - 22 Jan 2021

Cited by 3 | Viewed by 2446

Abstract

Due to the intensive process of road construction or rehabilitation of pavement caused by an increase in traffic volume, in the field of rigid pavement design and research in Romania, we can say that there is a need to improve the design method. In the last decade, more and more researchers have been concerned about climate change and the increase in traffic volume; hence, there is a need for a renewal of the climatological, as well as traffic, databases because these are part of the input data for the design process. The design method currently used in Romania for jointed plain concrete pavement design is NP081/2002. The limitation of the data and the lack of lifetime estimation of structural and functional performance are the main aspects that need to be addressed in the new design procedure. The Mechanistic–Empirical Pavement Design (MEPDG) method offers the possibility of the design of pavement structures by estimating the structural and functional performances. This paper aims to obtain a comparative study of these two methods for the analysis of the input data collected from the field corresponding to the three failure criteria, while the symmetry of the characteristics of the material and their asymmetrical thicknesses are compared, thus contributing to the design of viable and long-lasting pavement structures using a rigid pavement with the specific characteristics of the mountainous area in northeastern Romania on the national road DN17 Suceava—Vatra Dornei. The novelty of this study consists of the implementation of the mechanistic–empirical method MEPDG instead of the old NP081/2002 method used in Romania. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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13 pages, 5637 KiB

Open AccessArticle

Improving Room Carrying Capacity within Built Environments in the Context of COVID-19

by Luis Bañón and Carlos Bañón

Symmetry 2020, 12(10), 1683; https://doi.org/10.3390/sym12101683 - 14 Oct 2020

Cited by 13 | Viewed by 2823

Abstract

The COVID-19 pandemic that has struck the world since March 2019 has established an unusual modus operandi for all of us. During this transient situation, some of the activities have been severely altered, especially those which are performed in indoor spaces such as classrooms, restaurants, or libraries. As physical distance is mandatory in most countries, the capacity of these places has been severely reduced, causing unsustainable economic and logistical issues. This work aims to analyze the possible ways of distributing seats in symmetrical spaces for different uses and room sizes. For that purpose, the classical seat arrangement in rows and columns is compared with an equilateral triangle-based seat pattern, which is proposed as a better solution in most cases. Results show that a greater number of seats is achieved in most situations using the proposed patterns, with mean increases of 13% and peaks from 25% to 50% in some specific circumstances. A discussion about an optimized layout, shape and size of the furniture used in multiple seat tables is included. The outcome shall generate a positive impact on schools, colleges, restaurants, libraries, and similar built environments where seating capacity is crucial. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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16 pages, 4537 KiB

Open AccessArticle

Time Series Effect on Surface Deformation above Goaf Area with Multiple-Seam Mining

by Zhenyue Shi, Qingbiao Wang, Pu Wang, Donglin He, Yun Bai and Hongyue You

Symmetry 2020, 12(9), 1428; https://doi.org/10.3390/sym12091428 - 28 Aug 2020

Cited by 6 | Viewed by 1758

Abstract

The surface subsidence caused by coal mining is a large area, and computer simulation is a fast and intuitive method, which can help us understand the macroscopic subsidence law. The mined-out area left over by coal mining is not disposed of appropriately for a long time. Thus, it can easily cause ground subsidence, collapse, or spot cracking, especially when mining multiple coal seams, which seriously restricts the construction and safety of the near-surface rock and soil layers. Based on the engineering background of five-layer coal mining in the Beibu Coal Mine of Laiwu City, a “Fast Lagrangian Analysis of Continua in 3D” numerical calculation model was established. The model was used to analyze the surface deformation indexes of four groups with different mining sequences in multiple coal seams, revealing the sequence effects of mining time on the surface deformation law in the goaf collapse areas, hence obtaining optimal mining sequences. The results showed that the four groups of mining sequences (including vertical settlement and horizontal deformation) have stable surface deformation centers, but the deformation ranges and amounts are quite different. The settlement deformation is the main difference. Mining sequence I has the largest deformation of 62.7 cm, followed by mining sequence III. Mining sequences II and IV are basically the same, at only 22% of the value of mining sequence 1. A multi-index analysis of the surface deformation curve including the inflection point, stagnation point, and slope showed that the larger the surface deformation, the more evident the change of the curve (concave or convex) and slope, the more uneven the foundation stress, the more severe the damage to the surface structures, and the less suitable the surface construction. Finally, upon analyzing the indicators of surface stability and adaptability, mining sequence IV was indicated as the optimal scheme. It is suggested that an optimal mining sequence should be appropriately selected before the mining of multiple coal seams. The research results can provide effective guidance for addressing surface deformations under similar geological conditions, and can provide scientific evaluations for the safety and stability of surface buildings and structures, leading to considerable economic and social benefits. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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14 pages, 6015 KiB

Open AccessArticle

Bi-Directional Filter for the Removal of Lines and Cracks in Images

by Ali Said Awad

Symmetry 2020, 12(8), 1280; https://doi.org/10.3390/sym12081280 - 02 Aug 2020

Cited by 1 | Viewed by 2444

Abstract

In this paper, a method for the removal of noisy lines and cracks corrupted by different noise types is explored, using a cascade of filtering cycles based on the principle of symmetry among neighboring pixels. Each filtering cycle includes a filter in two perpendicular directions, one horizontal and the other vertical. Any pixel, to be deemed original, should have a number of symmetric pixels within its neighboring pixels greater than the number specified by the condition set for each direction in all the filters. Since the conditions of each filter increase gradually from one cycle to the next, it becomes more difficult for a noisy pixel to satisfy the filter conditions in each filtering cycle, while an original pixel can easily satisfy the conditions in all the filtering cycles. The reason is that a noisy pixel has a random value and therefore faces difficulty in finding a sufficient number of symmetric pixels in each direction, while an original one has a value correlated with the values of its neighboring pixels. Extensive simulation experiments prove that the proposed method efficiently detects and restores different noisy lines and cracks of different shape and thickness. Also, it retains the image details and outperforms other well-known algorithms, both objectively and subjectively. More specifically, the proposed algorithm achieves restoration performance better than the other known methods by ≥0.81dB in all simulation experiments. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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12 pages, 4851 KiB

Open AccessArticle

Design and Optimization of Plasmon Resonance Sensor Based on Micro–Nano Symmetrical Localized Surface

by Fengyu Yin, Jin Liu, Haima Yang, Aleksey Kudreyko and Bo Huang

Symmetry 2020, 12(5), 841; https://doi.org/10.3390/sym12050841 - 20 May 2020

Cited by 4 | Viewed by 2585

Abstract

Surface Plasma resonance (SPR) sensors combined with biological receptors are widely used in biosensors. Due to limitations of measurement techniques, small-scale, low accuracy, and sensitivity to the refractive index of solution in traditional SPR prism sensor arise. As a consequence, it is difficult to launch commercial production of SPR sensors. The theory of localized surface plasmon resonance (LSPR) developed based on SPR theory has stronger coupling ability to near-field photons. Based on the LSPR sensing theory, we propose a submicron-sized golden-disk and graphene composite structure. By varying the thickness and diameter of the array disk, the performance of the LSPR sensor can be optimized. A graphene layer sandwiched between the golden-disk and the silver film can prevent the latter from oxidizing. Symmetrical design enables high-low concentration of dual-channel distributed sensing. As the fixed light source, we use a 632.8-nm laser. A golden nano-disk with 45 nm thickness and 70 nm radius is designed, using a finite difference time domain (FDTD) simulation system. When the incident angle is 42°, the figure of merit (FOM) reaches 8826, and the measurable refractive index range reaches 0.2317. Full article

(This article belongs to the Special Issue Symmetry in Engineering Sciences Ⅲ)

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