Previous Issue
Volume 11, August

Table of Contents

Symmetry, Volume 11, Issue 9 (September 2019)

  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Readerexternal link to open them.
Order results
Result details
Select all
Export citation of selected articles as:
Open AccessArticle
A Modified Equation for Thickness of the Film Fabricated by Spin Coating
Symmetry 2019, 11(9), 1183; https://doi.org/10.3390/sym11091183 (registering DOI) - 18 Sep 2019
Abstract
According to the equation for Newtonian fluids, the film thickness after spin coating is determined by five parameters: angular velocity, spin coating time, viscosity, density of the coating material, and initial thickness of the material before spin coating. The spin coating process is [...] Read more.
According to the equation for Newtonian fluids, the film thickness after spin coating is determined by five parameters: angular velocity, spin coating time, viscosity, density of the coating material, and initial thickness of the material before spin coating. The spin coating process is commonly controlled by adjusting only the angular velocity parameter and the coating time in the Newtonian expression. However, the measured coating thickness obtained is then compared to the theoretical thickness calculated from the Newtonian fluid equation. The measured coating thickness usually varies somewhat from the theoretical thickness; further details are described in Section 1. Thus, the Newtonian fluid equation must be modified to better represent the actual film thickness. In this paper, we derive a new formula for the spin coating film thickness, which is based on the equation for Newtonian fluids, but modified to better represent film thicknesses obtained experimentally. The statistical analysis is performed to verify our modifications. Full article
(This article belongs to the Special Issue Nonlinear, Convex, Nonsmooth, Functional Analysis in Symmetry)
Show Figures

Figure 1

Open AccessArticle
Application of the Analytic Hierarchy Process and Grey Relational Analysis for Vendor Selection of Spare Parts Planning Software
Symmetry 2019, 11(9), 1182; https://doi.org/10.3390/sym11091182 (registering DOI) - 18 Sep 2019
Abstract
The success of after-sales services fundamentally depends on the possibility of symmetry balancing needs, supply and customer satisfaction. Spare parts planning (SPP) software selection is an investment in balancing the symmetry of inventory control, which directly affects the success of after-sales services. This [...] Read more.
The success of after-sales services fundamentally depends on the possibility of symmetry balancing needs, supply and customer satisfaction. Spare parts planning (SPP) software selection is an investment in balancing the symmetry of inventory control, which directly affects the success of after-sales services. This paper presents the analytic hierarchy process (AHP) and grey relational analysis (GRA) as potential multi-criteria decision making (MCDM) methods for software selection. The application of these methods can be decreased by decision-makers’ subjectivity, which leads to consistency and symmetry in the weight values of the criteria. The criteria were evaluated solely based on system functions by business consultants with respect to the modularity of the software to meet various business requirements, distinguishing this paper from other papers that focus on the financial aspects of selecting software. The results suggest that the AHP and GRA are feasible methods for software selection that effectively integrate consultants’ experience to identify the suitable software and the most important function for adoption in real businesses. The findings of our data suggest that inventory optimization is the most important function of SPP software, as the demand forecasting function may be subjective. In conclusion, this paper represents a bridge between practitioners and researchers. Full article
Show Figures

Graphical abstract

Open AccessArticle
LCA/LCC Model for Evaluation of Pump Units in Water Distribution Systems
Symmetry 2019, 11(9), 1181; https://doi.org/10.3390/sym11091181 - 18 Sep 2019
Viewed by 19
Abstract
In this multidisciplinary research, an LCA/LCC model is developed for assessing the costs, energy consumption, and greenhouse gas (GHG) emissions during the pump unit lifecycles in drinking water distribution systems (WDS). The presented methodology includes the pump, motor, and variable frequency drive monitoring [...] Read more.
In this multidisciplinary research, an LCA/LCC model is developed for assessing the costs, energy consumption, and greenhouse gas (GHG) emissions during the pump unit lifecycles in drinking water distribution systems (WDS). The presented methodology includes the pump, motor, and variable frequency drive monitoring as a system (pump unit), through their life-cycle stages: the manufacturing stage, the exploitation stage, and the disposal stage at the end of their life-cycle. The developed model also analyses other processes such as the maintenance, testing, and reconstruction of the pump unit. Demonstration of the presented methodology was performed using the pump unit of an operating WDS system in different scenarios, in order to illustrate the proper application of this model. The obtained results show that the application of pump units is justified in terms of energy consumption. The results also show that 93%–94% of the consumed energy and the LCC costs are related to the pump operating costs, while the rest are related to auxiliary operations. The findings show that various countries can have considerably different prices of electrical energy and different GHG emissions that depend on the source of electric energy. The implemented model incorporates some of the symmetries that are commonly found in the mathematical models of water distribution systems. Finally, the results of pump unit exploitation within the WDS have been used to show the impact of such plants on different levels of energy consumption, GHG emissions, and LCC production. Full article
Show Figures

Graphical abstract

Open AccessArticle
Comparison of Noether Symmetries and First Integrals of Two-Dimensional Systems of Second Order Ordinary Differential Equations by Real and Complex Methods
Symmetry 2019, 11(9), 1180; https://doi.org/10.3390/sym11091180 - 17 Sep 2019
Viewed by 111
Abstract
Noether symmetries and first integrals of a class of two-dimensional systems of second order ordinary differential equations (ODEs) are investigated using real and complex methods. We show that first integrals of systems of two second order ODEs derived by the complex Noether approach [...] Read more.
Noether symmetries and first integrals of a class of two-dimensional systems of second order ordinary differential equations (ODEs) are investigated using real and complex methods. We show that first integrals of systems of two second order ODEs derived by the complex Noether approach cannot be obtained by the real methods. Furthermore, it is proved that a complex method can be extended to larger systems and higher order. Full article
(This article belongs to the Special Issue Noether's Theorem and Symmetry)
Open AccessArticle
Abnormal Water Quality Monitoring Based on Visual Sensing of Three-Dimensional Motion Behavior of Fish
Symmetry 2019, 11(9), 1179; https://doi.org/10.3390/sym11091179 - 17 Sep 2019
Viewed by 108
Abstract
In the context of the problem of water pollution, the movement characteristics and patterns of fish under normal water quality and abnormal water quality are clearly different. This paper proposes a biological water quality monitoring method combining three-dimensional motion trajectory synthesis and integrated [...] Read more.
In the context of the problem of water pollution, the movement characteristics and patterns of fish under normal water quality and abnormal water quality are clearly different. This paper proposes a biological water quality monitoring method combining three-dimensional motion trajectory synthesis and integrated learning. The videos of the fish movement are captured by two cameras, and the Kuhn-Munkres (KM) algorithm is used to match the target points of the fish body. The Kalman filter is used to update the current state and find the optimal tracking position as the tracking result. The Kernelized Correlation Filters (KCF) algorithm compensates the targets that are lost in the tracking process and collision or occlusion in the movement process, reducing the errors caused by illumination, occlusion and water surface fluctuation effectively. This algorithm can directly obtain the target motion trajectory, avoiding the re-extraction from the centroid point in the image sequence, which greatly improves the efficiency. In order to avoid the one-sidedness of the two-dimensional trajectory, the experiment combines the pixel coordinates of different perspectives into three-dimensional trajectory pixel coordinates, so as to provide a more authentic fish swimming trajectory. We then select a representative positive and negative sample data set; the number of data sets should have symmetry. The base classifier capable of identifying different water quality is obtained by training. Finally, support vector machine(SVM), eXtreme Gradient Boosting (XGBoost) and pointnet based classifiers are combined into strong classifiers through integrated learning. The experimental results show that the integrated learning model can reflect the water quality effectively and accurately under the three-dimensional trajectory pixel coordinates of fish, and the recognition rate of water quality is above 95%. Full article
Show Figures

Figure 1

Open AccessArticle
Commuting Graphs, C(G, X) in Symmetric Groups Sym(n) and Its Connectivity
Symmetry 2019, 11(9), 1178; https://doi.org/10.3390/sym11091178 - 17 Sep 2019
Viewed by 91
Abstract
A commuting graph is a graph denoted by C ( G , X ) where G is any group and X, a subset of a group G, is a set of vertices for C ( G , X ) . Two [...] Read more.
A commuting graph is a graph denoted by C ( G , X ) where G is any group and X, a subset of a group G, is a set of vertices for C ( G , X ) . Two distinct vertices, x , y X , will be connected by an edge if the commutativity property is satisfied or x y = y x . This study presents results for the connectivity of C ( G , X ) when G is a symmetric group of degree n, Sym ( n ) , and X is a conjugacy class of elements of order three in G. Full article
Show Figures

Figure 1

Open AccessArticle
Converging Cylindrical Symmetric Shock Waves in a Real Medium with a Magnetic Field
Symmetry 2019, 11(9), 1177; https://doi.org/10.3390/sym11091177 - 17 Sep 2019
Viewed by 101
Abstract
The topic “converging shock waves” is quite useful in Inertial Confinement Fusion (ICF). Most of the earlier studies have assumed that the medium of propagation is ideal. However, due to very high temperature at the axis of convergence, the effect of medium on [...] Read more.
The topic “converging shock waves” is quite useful in Inertial Confinement Fusion (ICF). Most of the earlier studies have assumed that the medium of propagation is ideal. However, due to very high temperature at the axis of convergence, the effect of medium on shock waves should be taken in account. We have considered a problem of propagation of cylindrical shock waves in real medium. Magnetic field has been assumed in axial direction. It has been assumed that electrical resistance is zero. The problem can be represented by a system of hyperbolic Partial Differential Equations (PDEs) with jump conditions at the shock as the boundary conditions. The Lie group theoretic method has been used to find solutions to the problem. Lie’s symmetric method is quite useful as it reduces one-dimensional flow represented by a system of hyperbolic PDEs to a system of Ordinary Differential Equations (ODEs) by means of a similarity variable. Infinitesimal generators of Lie’s group transformation have been obtained by invariant conditions of the governing and boundary conditions. These generators involves arbitrary constants that give rise to different possible cases. One of the cases has been discussed in detail by writing reduced system of ODEs in matrix form. Cramer’s rule has been used to find the solution of system in matrix form. The results are presented in terms of figures for different values of parameters. The effect of non-ideal medium on the flow has been studied. Guderley’s rule is used to compute similarity exponents for cylindrical shock waves, in gasdynamics and in magnetogasdynamics (ideal medium), in order to set up a comparison with the published work. The computed values are very close to the values in published articles. Full article
(This article belongs to the Special Issue Matrices and Symmetry)
Show Figures

Figure 1

Open AccessArticle
A Novel Linear Antenna Synthesis for Linear Dispersion Codes Based on an Innovative HYBRID Genetic Algorithm
Symmetry 2019, 11(9), 1176; https://doi.org/10.3390/sym11091176 - 17 Sep 2019
Viewed by 103
Abstract
As far as taking-away of the symmetry constraints is concerned, as a scientifically symmetry problem, the global synthesis for antenna arrays that produce the desired radiation pattern is also a highly nonlinear optimization issue in fact. Besides this, the built criteria offer the [...] Read more.
As far as taking-away of the symmetry constraints is concerned, as a scientifically symmetry problem, the global synthesis for antenna arrays that produce the desired radiation pattern is also a highly nonlinear optimization issue in fact. Besides this, the built criteria offer the reasonable power patterns. The consequent synthesis could be implemented by looking for a nominal pattern. When the criteria are already sufficient, it can simply do the whole synthesis process. To utilize multiple antennae, a method to choose a transmit antenna for the linear dispersion codes (LDC-TAS) is implemented in this paper. The authors used the max–min-post- signal to noise ratio (SNR) criteria to select these optimal transmitting antennae while this dependent, linear receiver is applied to the varying and slow channel. The simulated results illustrate that this max–min-post-SNR criterion outperforms the Bell Labs layered space time transmitting antenna selection (BLAST-TAS) applying the same spectral efficiency than space–time block codes (STBC)-TAS in the environment with low SNR. Furthermore, once the M antennae are selected under the selection criteria, a max–min-post-SNR rule, a novel linear antenna synthesis to linear dispersion codes on the basis of an innovative HYBRID (of mixed characters or solutions) genetic algorithm has been presented and evaluated to formulate and address the optimal problem to non-uniformly spaced and linear arrays. The restricted side-lobes level, the main-lobe width, and the shaped beam pattern are contemporarily concerned via maximizing a pretty suitable cost function through the innovational advanced genetic-algorithm-based algorithm. The method proposed in this paper can provide flexibility and a simple insertion of the a priori knowledge under a small computing pressure. At last, a computing simulation is completed well and the results are shown. It should be noticed that some extensions of the presented method could also be easily utilized without an obvious increase in the algorithm complexity. Full article
Show Figures

Figure 1

Open AccessArticle
Optimization of Energetic Train Cooperation
Symmetry 2019, 11(9), 1175; https://doi.org/10.3390/sym11091175 - 16 Sep 2019
Viewed by 139
Abstract
In the article, possible ways of using energy recovered during regenerative braking of trains are presented. It is pointed out that the return of recovered electricity directly to the catenary and its use in the energy cooperation of vehicles can be a no-cost [...] Read more.
In the article, possible ways of using energy recovered during regenerative braking of trains are presented. It is pointed out that the return of recovered electricity directly to the catenary and its use in the energy cooperation of vehicles can be a no-cost method (without additional infrastructure). The method of energy cooperation between trains and its main assumptions, that uses the law of conservation of energy, are described in detail. An original model is proposed which assumes optimization by controlling the train arrival time at the station within the technical time reserve. Optimization method was used metaheuristic and adapted swarm algorithm called the firefly algorithm. An exemplary simulation of the energy cooperation of trains for selected stops of a double-track railway line of the Tricity Rapid Urban Railway has been done and the obtained results are presented. Finally, in discussion and conclusions, the results were summarized and the significance of the development of the discussed method for transport rationalization was presented. Full article
Open AccessArticle
Dynamical Properties of Dark Energy Models in Fractal Universe
Symmetry 2019, 11(9), 1174; https://doi.org/10.3390/sym11091174 - 16 Sep 2019
Viewed by 132
Abstract
In this paper, we consider the flat FRW spacetime filled with interacting dark energy and dark matter in fractal universe. We work with the three models of dark energy named as Tsallis, Renyi and Sharma–Mittal. We investigate different cosmological implications such as equation [...] Read more.
In this paper, we consider the flat FRW spacetime filled with interacting dark energy and dark matter in fractal universe. We work with the three models of dark energy named as Tsallis, Renyi and Sharma–Mittal. We investigate different cosmological implications such as equation of state parameter, squared speed of sound, deceleration parameter, statefinder parameters, ω e f f - ω e f f ´ (where prime indicates the derivative with respect to ln a , and a is cosmic scale factor) plane and Om diagnostic. We explore these parameters graphically to study the evolving universe. We compare the consistency of dark energy models with the accelerating universe observational data. All three models are stable in fractal universe and support accelerated expansion of the universe. Full article
(This article belongs to the Special Issue Beyond the Standard Cosmological Model in the Multi-messenger Era)
Open AccessArticle
Path Mapping Approach for Network Function Virtualization Resource Allocation with Network Function Decomposition Support
Symmetry 2019, 11(9), 1173; https://doi.org/10.3390/sym11091173 - 16 Sep 2019
Viewed by 209
Abstract
Recently, Network Function Virtualization (NFV) and Software Defined Networking (SDN) have attracted many mobile operators. For the flexible deployment of Network Functions (NFs) in an NFV environment, NF decompositions and control/user plane separation have been introduced in the literature. That is to map [...] Read more.
Recently, Network Function Virtualization (NFV) and Software Defined Networking (SDN) have attracted many mobile operators. For the flexible deployment of Network Functions (NFs) in an NFV environment, NF decompositions and control/user plane separation have been introduced in the literature. That is to map traditional functions into their corresponding Virtual Network Functions (VNFs). This mapping requires the NFV Resource Allocation (NFV-RA) for multi-path service graphs with a high number of virtual nodes and links, which is a complex NP-hard problem that inherited its complexity from the Virtual Network Embedding (VNE). This paper proposes a new path mapping approach to solving the NFV-RA problem for decomposed Network Service Chains (NSCs). The proposed solution has symmetrically considered optimizing an average embedding cost with an enhancement on average execution time. The proposed approach has been compared to two other existing schemes using 6 and 16 scenarios of short and long simulation runs, respectively. The impact of the number of nodes, links and paths of the service requests on the proposed scheme has been studied by solving more than 122,000 service requests. The proposed Integer Linear Programming (ILP) and heuristic schemes have reduced the execution time up to 39.58% and 6.42% compared to existing ILP and heuristic schemes, respectively. Moreover, the proposed schemes have also reduced the average embedding cost and increased the profit for the service providers. Full article
Show Figures

Graphical abstract

Open AccessArticle
Single-Qubit Driving Fields and Mathieu Functions
Symmetry 2019, 11(9), 1172; https://doi.org/10.3390/sym11091172 - 16 Sep 2019
Viewed by 129
Abstract
We report a new family of time-dependent single-qubit radiation fields for which the correspondent evolution operator can be disentangled in an exact way via the Wei–Norman formalism. Such fields are characterized in terms of the Mathieu functions. We show that the regions of [...] Read more.
We report a new family of time-dependent single-qubit radiation fields for which the correspondent evolution operator can be disentangled in an exact way via the Wei–Norman formalism. Such fields are characterized in terms of the Mathieu functions. We show that the regions of stability of the Mathieu functions determine the nature of the driving fields: For parameters in the stable region, the fields are oscillating, being able to be periodic under certain conditions. Whereas, for parameters in the instability region, the fields are pulse-like. In addition, in the stability region, this family admits solutions for evolution loops in quantum control. We obtain some prescriptions to reach such a control effect. Geometric phases in the evolution are also analyzed and discussed. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
Show Figures

Figure 1

Open AccessArticle
Multiple Slip Effects on Magnetohydrodynamic Axisymmetric Buoyant Nanofluid Flow above a Stretching Sheet with Radiation and Chemical Reaction
Symmetry 2019, 11(9), 1171; https://doi.org/10.3390/sym11091171 - 16 Sep 2019
Viewed by 118
Abstract
The present article investigates the effect of multiple slips on axisymmetric magnetohydrodynamics (MHD) buoyant nano-fluid flow over a stretching sheet with radiation and chemical effect. The non-linear partial differential equations were transformed to a non-linear control equation using an appropriate similarity transformation. The [...] Read more.
The present article investigates the effect of multiple slips on axisymmetric magnetohydrodynamics (MHD) buoyant nano-fluid flow over a stretching sheet with radiation and chemical effect. The non-linear partial differential equations were transformed to a non-linear control equation using an appropriate similarity transformation. The governing equations were solved through the finite element method. The influence of physical parameters such as multiple slips, magnetic, thermal radiation, Prandtl number, stretching, Brownian motion, thermophoresis, Schmidt number, Lewis number and chemical reaction on the radial velocity, temperature, solutal concentration and nano-fluid volume fraction profile were investigated. We noted that the boundary layers increases in the presence of multiple slip effects whereas, the effect of thermal slip on Nusselt number increases with the increasing values of magnetic and thermal radiation. To verify the convergence of the numerical solution, the computations were made by reducing the mesh size. Finally, our results are parallel to previous scholarly contributions. Full article
(This article belongs to the Special Issue Future and Prospects in Non-Newtonian and Nanofluids)
Show Figures

Figure 1

Open AccessFeature PaperArticle
Symmetry at the Cellular Mesoscale
Symmetry 2019, 11(9), 1170; https://doi.org/10.3390/sym11091170 - 16 Sep 2019
Viewed by 99
Abstract
Symmetry plays a functional role in the structure and action of biomolecules and their associations and interactions in living cells. This symmetry is a natural consequence of the evolutionary mechanisms that lead to the development of life, and it ranges from perfect point-group [...] Read more.
Symmetry plays a functional role in the structure and action of biomolecules and their associations and interactions in living cells. This symmetry is a natural consequence of the evolutionary mechanisms that lead to the development of life, and it ranges from perfect point-group symmetry in protein oligomers to more approximate symmetries in the higher-order mesoscale structure of cellular environments. Full article
(This article belongs to the Special Issue Symmetry in Molecular Biology)
Show Figures

Figure 1

Open AccessArticle
The Weighted Surplus Division Value for Cooperative Games
Symmetry 2019, 11(9), 1169; https://doi.org/10.3390/sym11091169 - 16 Sep 2019
Viewed by 107
Abstract
The weighted surplus division value is defined in this paper, which allocates to each player his individual worth and then divides the surplus payoff with respect to the weight coefficients. This value can be characterized from three different angles. First, it can be [...] Read more.
The weighted surplus division value is defined in this paper, which allocates to each player his individual worth and then divides the surplus payoff with respect to the weight coefficients. This value can be characterized from three different angles. First, it can be obtained analogously to the scenario of getting the procedural value whereby the surplus is distributed among all players instead of among the predecessors. Second, endowing the exogenous weight to the surplus brings about the asymmetry of the distribution. We define the disweighted variance of complaints to remove the effect of the weight and prove the weighted surplus division value is the unique solution of an optimization model. Lastly, the paper offers axiomatic characterizations of the weighted surplus division value through proposing new properties, including the ω -symmetry for zero-normalized game and individual equity. Full article
Open AccessArticle
A Note on degenerate Euler and Bernoulli Polynomials of Complex Variable
Symmetry 2019, 11(9), 1168; https://doi.org/10.3390/sym11091168 - 16 Sep 2019
Viewed by 151
Abstract
Recently, the so-called new type Euler polynomials have been studied without considering Euler polynomials of a complex variable. Here we study degenerate versions of these new type Euler polynomials. This has been done by considering the degenerate Euler polynomials of a complex variable. [...] Read more.
Recently, the so-called new type Euler polynomials have been studied without considering Euler polynomials of a complex variable. Here we study degenerate versions of these new type Euler polynomials. This has been done by considering the degenerate Euler polynomials of a complex variable. We also investigate corresponding ones for Bernoulli polynomials in the same manner. We derive some properties and identities for those new polynomials. Here we note that our result gives an affirmative answer to the question raised by the reviewer of the paper. Full article
Open AccessArticle
Fast Finger Vein Recognition Based on Sparse Matching Algorithm under a Multicore Platform for Real-Time Individuals Identification
Symmetry 2019, 11(9), 1167; https://doi.org/10.3390/sym11091167 - 15 Sep 2019
Viewed by 180
Abstract
Nowadays, individual identification is a problem in many private companies, but also in governmental and public order entities. Currently, there are multiple biometric methods, each with different advantages. Finger vein recognition is a modern biometric technique, which has several advantages, especially in terms [...] Read more.
Nowadays, individual identification is a problem in many private companies, but also in governmental and public order entities. Currently, there are multiple biometric methods, each with different advantages. Finger vein recognition is a modern biometric technique, which has several advantages, especially in terms of security and accuracy. However, image deformations and time efficiency are two of the major limitations of state-of-the-art contributions. In spite of affine transformations produced during the acquisition process, the geometric structure of finger vein images remains invariant. This consideration of the symmetry phenomena presented in finger vein images is exploited in the present work. We combine an image enhancement procedure, the DAISY descriptor, and an optimized Coarse-to-fine PatchMatch (CPM) algorithm under a multicore parallel platform, to develop a fast finger vein recognition method for real-time individuals identification. Our proposal provides an effective and efficient technique to obtain the displacement between finger vein images and considering it as discriminatory information. Experimental results on two well-known databases, PolyU and SDUMLA, show that our proposed approach achieves results comparable to deformation-based techniques of the state-of-the-art, finding statistical differences respect to non-deformation-based approaches. Moreover, our method highly outperforms the baseline method in time efficiency. Full article
Show Figures

Graphical abstract

Open AccessArticle
Simulation of Passenger Evacuation Process in Cruise Ships Based on A Multi-Grid Model
Symmetry 2019, 11(9), 1166; https://doi.org/10.3390/sym11091166 - 15 Sep 2019
Viewed by 148
Abstract
The evacuation of the cruise ship is directly related to the safety of passengers during accidents. The method for avoiding and reducing casualties in accidents has become a research frontier of maritime safety. This paper presents the simulation of a passenger evacuation process [...] Read more.
The evacuation of the cruise ship is directly related to the safety of passengers during accidents. The method for avoiding and reducing casualties in accidents has become a research frontier of maritime safety. This paper presents the simulation of a passenger evacuation process using a multi-grid model. In the model, directions of passengers’ movement are extended and the relationship between passengers’ orientation and the walking speed under the inclining condition is also analyzed in detail. Considering the space layout, the attraction of the mainstream crowd and exclusion between individuals, the probability of passengers’ transfer between grids is established. The deck of the cruise ship is taken as the evacuation scenario and four parameters are defined for the scenario according to International Maritime Organization (IMO) guidelines. The process of evacuation in the cruise ship is simulated under upright and inclining conditions. Through the analysis of simulation results, evacuation bottleneck data and the relation between inclined angles and evacuation time are obtained. This work may provide a reference for formulating emergency evacuation plans for cruise ships. Full article
Show Figures

Figure 1

Open AccessArticle
On the Secure Total Domination Number of Graphs
Symmetry 2019, 11(9), 1165; https://doi.org/10.3390/sym11091165 - 15 Sep 2019
Viewed by 158
Abstract
A total dominating set D of a graph G is said to be a secure total dominating set if for every vertex u V ( G ) \ D , there exists a vertex v D , which is adjacent to [...] Read more.
A total dominating set D of a graph G is said to be a secure total dominating set if for every vertex u V ( G ) \ D , there exists a vertex v D , which is adjacent to u, such that ( D \ { v } ) { u } is a total dominating set as well. The secure total domination number of G is the minimum cardinality among all secure total dominating sets of G. In this article, we obtain new relationships between the secure total domination number and other graph parameters: namely the independence number, the matching number and other domination parameters. Some of our results are tight bounds that improve some well-known results. Full article
(This article belongs to the Special Issue Protection of Graphs)
Show Figures

Figure 1

Open AccessArticle
Feature Selection for Blood Glucose Level Prediction in Type 1 Diabetes Mellitus by Using the Sequential Input Selection Algorithm (SISAL)
Symmetry 2019, 11(9), 1164; https://doi.org/10.3390/sym11091164 - 14 Sep 2019
Viewed by 193
Abstract
Feature selection is a primary exercise to tackle any forecasting task. Machine learning algorithms used to predict any variable can improve their performance by lessening their computational effort with a proper dataset. Anticipating future glycemia in type 1 diabetes mellitus (DM1) patients provides [...] Read more.
Feature selection is a primary exercise to tackle any forecasting task. Machine learning algorithms used to predict any variable can improve their performance by lessening their computational effort with a proper dataset. Anticipating future glycemia in type 1 diabetes mellitus (DM1) patients provides a baseline in its management, and in this task, we need to carefully select data, especially now, when novel wearable devices offer more and more information. In this paper, a complete characterization of 25 diabetic people has been carried out, registering innovative variables like sleep, schedule, or heart rate in addition to other well-known ones like insulin, meal, and exercise. With this ground-breaking data compilation, we present a study of these features using the Sequential Input Selection Algorithm (SISAL), which is specially prepared for time series data. The results rank features according to their importance, regarding their relevance in blood glucose level prediction as well as indicating the most influential past values to be taken into account and distinguishing features with person-dependent behavior from others with a common performance in any patient. These ideas can be used as strategies to select data for predicting glycemia depending on the availability of computational power, required speed, or required accuracy. In conclusion, this paper tries to analyze if there exists symmetry among the different features that can affect blood glucose levels, that is, if their behavior is symmetric in terms of influence in glycemia. Full article
Open AccessArticle
Covering Graphs, Magnetic Spectral Gaps and Applications to Polymers and Nanoribbons
Symmetry 2019, 11(9), 1163; https://doi.org/10.3390/sym11091163 - 14 Sep 2019
Viewed by 170
Abstract
In this article, we analyze the spectrum of discrete magnetic Laplacians (DML) on an infinite covering graph G ˜ G = G ˜ / Γ with (Abelian) lattice group Γ and periodic magnetic potential β ˜ . We give sufficient conditions for [...] Read more.
In this article, we analyze the spectrum of discrete magnetic Laplacians (DML) on an infinite covering graph G ˜ G = G ˜ / Γ with (Abelian) lattice group Γ and periodic magnetic potential β ˜ . We give sufficient conditions for the existence of spectral gaps in the spectrum of the DML and study how these depend on β ˜ . The magnetic potential can be interpreted as a control parameter for the spectral bands and gaps. We apply these results to describe the spectral band/gap structure of polymers (polyacetylene) and nanoribbons in the presence of a constant magnetic field. Full article
(This article belongs to the Special Issue New trends on Symmetry and Topology in Quantum Mechanics)
Open AccessArticle
UAV Group Formation Collision Avoidance Method Based on Second-Order Consensus Algorithm and Improved Artificial Potential Field
Symmetry 2019, 11(9), 1162; https://doi.org/10.3390/sym11091162 - 13 Sep 2019
Viewed by 121
Abstract
The problem of collision avoidance of an unmanned aerial vehicle (UAV) group is studied in this paper. A collision avoidance method of UAV group formation based on second-order consensus algorithm and improved artificial potential field is proposed. Based on the method, the UAV [...] Read more.
The problem of collision avoidance of an unmanned aerial vehicle (UAV) group is studied in this paper. A collision avoidance method of UAV group formation based on second-order consensus algorithm and improved artificial potential field is proposed. Based on the method, the UAV group can form a predetermined formation from any initial state and fly to the target position in normal flight, and can avoid collision according to the improved smooth artificial potential field method when encountering an obstacle. The UAV group adopts the “leader–follower” strategy, that is, the leader UAV is the controller and flies independently according to the mission requirements, while the follower UAV follows the leader UAV based on the second-order consensus algorithm and formations gradually form during the flight. Based on the second-order consensus algorithm, the UAV group can achieve formation maintenance easily and the Laplacian matrix used in the algorithm is symmetric for an undirected graph. In the process of obstacle avoidance, the improved artificial potential field method can solve the jitter problem that the traditional artificial potential field method causes for the UAV and avoids violent jitter. Finally, simulation experiments of two scenarios were designed to verify the collision avoidance effect and formation retention effect of static obstacles and dynamic obstacles while the two UAV groups fly in opposite symmetry in the dynamic obstacle scenario. The experimental results demonstrate the effectiveness of the proposed method. Full article
Show Figures

Figure 1

Open AccessArticle
A Hybrid Active Filter Using the Backstepping Controller for Harmonic Current Compensation
Symmetry 2019, 11(9), 1161; https://doi.org/10.3390/sym11091161 - 12 Sep 2019
Viewed by 141
Abstract
This document presents a new hybrid combination of filters using passive and active elements because of the generalization in the use of non-linear loads that generate harmonics directly affecting the symmetry of energy transmission systems that influence the functioning of the electricity grid [...] Read more.
This document presents a new hybrid combination of filters using passive and active elements because of the generalization in the use of non-linear loads that generate harmonics directly affecting the symmetry of energy transmission systems that influence the functioning of the electricity grid and, consequently, the deterioration of power quality. In this context, active power filters represent one of the best solutions for improving power quality and compensating harmonic currents to get a symmetrical waveform. In addition, given the importance and occupation of the transmission network, it is necessary to control the stability of the system. Traditionally, passive filters were used to improve energy quality, but they have endured problems such as resonance, fixed remuneration, etc. In order to mitigate these problems, a hybrid HAPF active power filter is proposed combining a parallel active filter and a passive filter controlled by a backstepping algorithm strategy. This control strategy is compared with two other methods, namely the classical PI control, and the fuzzy logic control in order to verify the effectiveness and the level of symmetry of the backstepping controller proposed for the HAPF. The proposed backstepping controller inspires the notion of stability in Lyapunov’s sense. This work is carried out to improve the performance of the HAPF by the backstepping command. It perfectly compensates the harmonics according to standards. The results of simulations performed under the Matlab/Simulink environment show the efficiency and robustness of the proposed backstepping controller applied on HAPF, compared to other control methods. The HAPF with the backstepping controller shows a significant decrease in the THD harmonic distortion rate. Full article
(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)
Open AccessArticle
A Bi–LSTM and k-NN Based Method for Detecting Major Time Zones of Overloaded Vehicles
Symmetry 2019, 11(9), 1160; https://doi.org/10.3390/sym11091160 - 12 Sep 2019
Viewed by 142
Abstract
Overloaded vehicles such as large cargo trucks tend to cause large traffic accidents. Such traffic accidents often bring high mortality rates, including injuries and deaths, and cause fatal damage to road structures such as roads and bridges. Therefore, there is a vicious circle [...] Read more.
Overloaded vehicles such as large cargo trucks tend to cause large traffic accidents. Such traffic accidents often bring high mortality rates, including injuries and deaths, and cause fatal damage to road structures such as roads and bridges. Therefore, there is a vicious circle in which a lot of the budgets is spent for accident restoration and road maintenance. It is important to control overloaded vehicles that are around roads in urban areas. However, it often takes a lot of manpower to track down on overloaded vehicles at appropriate interception points during a specific time. Moreover, the drivers tend to avoid interception by bypassing the interception point, while exchanging interception information with each other. In this work, the main bridges in a city are chosen as the interception point. Since installing vehicle-weighing devices on the road surface is expensive and the devices cause frequent faults after the installation, inexpensive general-purpose Internet of Things (IoT) sensors, such as acceleration and gyroscope sensors, are installed on the bridges. First, assuming that the sensing value of the overloaded vehicle is different from the nonoverloaded vehicle, we investigate the difference in the sensed values between the overloaded and nonoverloaded vehicles. Then, based on the hypothesis, we propose a new method to identify prime time zones with overloaded vehicles. Technically, the proposed method comprises two steps. In the first step, we propose a new bridge traffic classification model using Bidirectional Long Short-Term Memory (Bi–LSTM) that automatically classifies time series data to either high or low traffic condition. The Bi–LSTM model has higher accuracy than existing neural network models because it has a symmetric neural network structure, by which input information can be processed in forward and backward directions. In the second step, we propose a new method of automatically identifying top-k time zones with many overloaded vehicles under the high traffic condition. It first uses the k-Nearest Neighbor (NN) algorithm to find the sensing value, most similar to the actual sensing value of the overloaded vehicle, in the high traffic cluster. According to the experimental results, there is a high difference of the sensing values between the overloaded and the nonoverloaded vehicle, through statistical verification. Also, the accuracy of the proposed method in the first step is ~75%, and the top-k time zones in which overloaded vehicles are crowded are identified automatically. Full article
Show Figures

Graphical abstract

Open AccessArticle
Chemometric Evaluation of the Link between Acute Toxicity, Health Issues and Physicochemical Properties of Silver Nanoparticles
Symmetry 2019, 11(9), 1159; https://doi.org/10.3390/sym11091159 - 11 Sep 2019
Viewed by 201
Abstract
The present study’s objective is to focus on some developments in the field of statistical models of a complex system, like nanoparticles responses in the environmental media. An important problem that still needs to be studied and interpreted is the relations between physicochemical [...] Read more.
The present study’s objective is to focus on some developments in the field of statistical models of a complex system, like nanoparticles responses in the environmental media. An important problem that still needs to be studied and interpreted is the relations between physicochemical parameters of the nanoparticles like primary size, primary hydrophobic diameter, zeta potential, etc. with respective toxicity values. It holds true especially for silver nanoparticle systems due to their known bactericidal effect and wide distribution in practice. The present study deals with the data for physicochemical and toxicity parameters of 94 different silver nanoparticle systems in order to reveal specific relations between physicochemical properties and acute toxicity readings using multivariate statistical methods. Searching for these specific relationships between physicochemical parameters and toxicity responses is the novel element in the present study. This has focused our study toward developing a model that describes the relationship between physicochemical properties and toxicity of silver NPs based on a dataset gathered from the literature. It is shown that the systems studied could be divided into four patterns (clusters) of similarity depending not only on the physicochemical indicators related to particles size but also by their acute toxicity. The acute toxicity is strongly correlated to the zeta potential of the particles if the whole data set is considered. Full article
(This article belongs to the Special Issue Chemometrics in Assessing Molecular Structures and Properties)
Show Figures

Figure 1

Open AccessArticle
Study on Stiffness-Oriented Cable Tension Distribution for a Symmetrical Cable-Driven Mechanism
Symmetry 2019, 11(9), 1158; https://doi.org/10.3390/sym11091158 - 11 Sep 2019
Viewed by 111
Abstract
In this paper, we focus on the issues pertaining to stiffness-oriented cable tension distribution
for a symmetrical 6-cable-driven spherical joint module (6-CSJM), which can be employed to construct
modular cable-driven manipulators. Due to the redundant actuation of the 6-CSJM, three cables are
employed [...] Read more.
In this paper, we focus on the issues pertaining to stiffness-oriented cable tension distribution
for a symmetrical 6-cable-driven spherical joint module (6-CSJM), which can be employed to construct
modular cable-driven manipulators. Due to the redundant actuation of the 6-CSJM, three cables are
employed for position regulation by adjusting the cable lengths, and the remaining three cables are
utilized for stiffness regulation by adjusting the cable tensions, i.e., the position and stiffness can be
regulated simultaneously. To increase the range of stiffness regulation, a variable stiffness device
(VSD) is designed, which is serially connected to the driving cable. Since the stiffness model of the
6-CSJM with VSDs is very complicated, it is difficult to directly solve the cable tensions from the
desired stiffness. The stiffness-oriented cable tension distribution issue is formulated as a nonlinear
constrained optimization problem, and the Complex method is employed to obtain optimal tension
distributions. Furthermore, to significantly improve the computation efficiency, a decision variable
elimination technique is proposed to deal with the equality constraints, which reduces decision variables
from 6 to 3. A comprehensive simulation study is conducted to verify the effectiveness of the proposed
method, showing that the 6-CSJM can accurately achieve the desired stiffness through cable tension
optimization. Full article
(This article belongs to the Special Issue Symmetry in Engineering Sciences II)
Open AccessReview
From Science to Practice: A Review of Laterality Research on Ungulate Livestock
Symmetry 2019, 11(9), 1157; https://doi.org/10.3390/sym11091157 - 11 Sep 2019
Viewed by 263
Abstract
In functional laterality research, most ungulate livestock species have until recently been mainly overlooked. However, there are many scientific and practical benefits of studying laterality in ungulate livestock. As social, precocial and domestic species, they may offer insight into the mechanisms involved in [...] Read more.
In functional laterality research, most ungulate livestock species have until recently been mainly overlooked. However, there are many scientific and practical benefits of studying laterality in ungulate livestock. As social, precocial and domestic species, they may offer insight into the mechanisms involved in the ontogeny and phylogeny of functional laterality and help to better understand the role of laterality in animal welfare. Until now, most studies on ungulate livestock have focused on motor laterality, but interest in other lateralized functions, e.g., cognition and emotions, is growing. Increasingly more studies are also focused on associations with age, sex, personality, health, stress, production and performance. Although the full potential of research on laterality in ungulate livestock is not yet exploited, findings have already shed new light on central issues in cognitive and emotional processing and laid the basis for potentially useful applications in future practice, e.g., stress reduction during human-animal interactions and improved assessments of health, production and welfare. Future research would benefit from further integration of basic laterality methodology (e.g., testing for individual preferences) and applied ethological approaches (e.g., established emotionality tests), which would not only improve our understanding of functional laterality but also benefit the assessment of animal welfare. Full article
(This article belongs to the Special Issue Brain Functional Lateralization in Animals)
Open AccessArticle
Hybrid Multi-Domain Analytical and Data-Driven Modeling for Feed Systems in Machine Tools
Symmetry 2019, 11(9), 1156; https://doi.org/10.3390/sym11091156 - 11 Sep 2019
Viewed by 169
Abstract
Position error-compensation control in the servo system of computerized numerical control (CNC) machine tools relies on accurate prediction of dynamic tracking errors of the machine tool feed system. In this paper, in order to accurately predict dynamic tracking errors, a hybrid modeling method [...] Read more.
Position error-compensation control in the servo system of computerized numerical control (CNC) machine tools relies on accurate prediction of dynamic tracking errors of the machine tool feed system. In this paper, in order to accurately predict dynamic tracking errors, a hybrid modeling method is proposed and a dynamic model of the ball screw feed system is developed. Firstly, according to the law of conservation of energy, a complete multi-domain system analytical model of a ball screw feed system was established based on energy flow. In order to overcome the uncertainties of the analytical model, then the data-driven model based on the back propagation (BP) neural network was established and trained using experimental data. Finally, the data-driven model was coupled with the multi-domain analytical model and the hybrid model was developed. The model was verified by experiment at different velocities and the results show that the prediction accuracy of the hybrid model reaches high levels. The hybrid modeling method combines the advantages of analytical modeling and data-driven modeling methods, and can significantly improve the feed system’s modeling accuracy. The research results of this paper are of great significance to improve the compensation control accuracy of CNC machine tools. Full article
Show Figures

Figure 1

Open AccessArticle
Low-Rank Multi-Channel Features for Robust Visual Object Tracking
Symmetry 2019, 11(9), 1155; https://doi.org/10.3390/sym11091155 - 11 Sep 2019
Viewed by 202
Abstract
Kernel correlation filters (KCF) demonstrate significant potential in visual object tracking by employing robust descriptors. Proper selection of color and texture features can provide robustness against appearance variations. However, the use of multiple descriptors would lead to a considerable feature dimension. In this [...] Read more.
Kernel correlation filters (KCF) demonstrate significant potential in visual object tracking by employing robust descriptors. Proper selection of color and texture features can provide robustness against appearance variations. However, the use of multiple descriptors would lead to a considerable feature dimension. In this paper, we propose a novel low-rank descriptor, that provides better precision and success rate in comparison to state-of-the-art trackers. We accomplished this by concatenating the magnitude component of the Overlapped Multi-oriented Tri-scale Local Binary Pattern (OMTLBP), Robustness-Driven Hybrid Descriptor (RDHD), Histogram of Oriented Gradients (HoG), and Color Naming (CN) features. We reduced the rank of our proposed multi-channel feature to diminish the computational complexity. We formulated the Support Vector Machine (SVM) model by utilizing the circulant matrix of our proposed feature vector in the kernel correlation filter. The use of discrete Fourier transform in the iterative learning of SVM reduced the computational complexity of our proposed visual tracking algorithm. Extensive experimental results on Visual Tracker Benchmark dataset show better accuracy in comparison to other state-of-the-art trackers. Full article
(This article belongs to the Special Issue Deep Learning-Based Biometric Technologies)
Show Figures

Figure 1

Open AccessArticle
ILRA: Novelty Detection in Face-Based Intervener Re-Identification
Symmetry 2019, 11(9), 1154; https://doi.org/10.3390/sym11091154 - 11 Sep 2019
Viewed by 166
Abstract
Transparency laws facilitate citizens to monitor the activities of political representatives. In this sense, automatic or manual diarization of parliamentary sessions is required, the latter being time consuming. In the present work, this problem is addressed as a person re-identification problem. Re-identification is [...] Read more.
Transparency laws facilitate citizens to monitor the activities of political representatives. In this sense, automatic or manual diarization of parliamentary sessions is required, the latter being time consuming. In the present work, this problem is addressed as a person re-identification problem. Re-identification is defined as the process of matching individuals under different camera views. This paper, in particular, deals with open world person re-identification scenarios, where the captured probe in one camera is not always present in the gallery collected in another one, i.e., determining whether the probe belongs to a novel identity or not. This procedure is mandatory before matching the identity. In most cases, novelty detection is tackled applying a threshold founded in a linear separation of the identities. We propose a threshold-less approach to solve the novelty detection problem, which is based on a one-class classifier and therefore it does not need any user defined threshold. Unlike other approaches that combine audio-visual features, an Isometric LogRatio transformation of a posteriori (ILRA) probabilities is applied to local and deep computed descriptors extracted from the face, which exhibits symmetry and can be exploited in the re-identification process unlike audio streams. These features are used to train the one-class classifier to detect the novelty of the individual. The proposal is evaluated in real parliamentary session recordings that exhibit challenging variations in terms of pose and location of the interveners. The experimental evaluation explores different configuration sets where our system achieves significant improvement on the given scenario, obtaining an average F measure of 71.29% for online analyzed videos. In addition, ILRA performs better than face descriptors used in recent face-based closed world recognition approaches, achieving an average improvement of 1.6% with respect to a deep descriptor. Full article
Show Figures

Graphical abstract

Previous Issue
Back to TopTop