12 pages, 944 KiB  
Article
Research on Spectrum Optimization Technology for a Wireless Communication System
by Mingxin Liu, Wei Xue, Peisong Jia, Sergey B. Makarov and Beiming Li
Symmetry 2020, 12(1), 34; https://doi.org/10.3390/sym12010034 - 23 Dec 2019
Cited by 16 | Viewed by 2553
Abstract
In this study, the principle of minimum spectral energy leakage is applied, and the mathematical model is also established by the general function through adding different constraints. To allow the target baseband signal to have a high-quality time-domain representation, it is assumed that [...] Read more.
In this study, the principle of minimum spectral energy leakage is applied, and the mathematical model is also established by the general function through adding different constraints. To allow the target baseband signal to have a high-quality time-domain representation, it is assumed that the baseband signal is an even function. The time-domain waveform has symmetry about the y-axis, and the objective function is obtained by Fourier series approximation. The frequency-domain characteristics of the baseband signals are obtained by adding the energy limitation condition and the boundary restriction condition. Limit a point at the appropriate position of the main lobe of the normalized energy spectral density function, and at the same time, limit the appropriate point at the first side lobe. The changes of the points modified the whole characteristic of the frequency-domain. To more conveniently compare the characteristics of the signal under different constraints, according to the symmetry of the frequency-domain of the signal, the normalized energy spectrum main lobe energy ratio is defined as a parameter, and thereby the spectral performance of the signal is discriminated by the size of this parameter. Through comparative analysis, the signal with the frequency-domain restriction conditions added has a larger normalized energy spectrum main lobe energy ratio. With increasing roll-off factor n, the energy ratio of the main energy spectrum of the normalized spectrum increases accordingly, i.e., the energy leakage is effectively suppressed. The baseband signal can be considered more suitable as a modern wireless communication system and can be obtained by adding a suitable restriction condition and establishing a model with a general function. Full article
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8 pages, 2594 KiB  
Article
A Hybrid Mechanism for Helicopters
by Kevin Kuan-Shun Chiu, Jeou-Long Lee, Ming-Lang Tseng, Rosslyn Hsiu-Ling Hsu and Yen-Jen Chen
Symmetry 2020, 12(1), 33; https://doi.org/10.3390/sym12010033 - 22 Dec 2019
Cited by 1 | Viewed by 3462
Abstract
This study successfully provides the empirical practicability of a hybrid mechanism for helicopters. A turbine engine and a set of electricity power systems can operate simultaneously and/or independently as a symmetric structure. The latter power source works as an immediate supplementary device if [...] Read more.
This study successfully provides the empirical practicability of a hybrid mechanism for helicopters. A turbine engine and a set of electricity power systems can operate simultaneously and/or independently as a symmetric structure. The latter power source works as an immediate supplementary device if the former one has malfunction. We look forward to promoting this experimental evidence in the helicopter industry. The ultimate purpose of this manuscript is to decrease the incidents of crashes and save people’s lives. Full article
(This article belongs to the Special Issue Symmetry in Mechanical Engineering)
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21 pages, 2816 KiB  
Article
MICKEY 2.0.85: A Secure and Lighter MICKEY 2.0 Cipher Variant with Improved Power Consumption for Smaller Devices in the IoT
by Ahmed Alamer, Ben Soh and David E. Brumbaugh
Symmetry 2020, 12(1), 32; https://doi.org/10.3390/sym12010032 - 22 Dec 2019
Cited by 7 | Viewed by 3494
Abstract
Lightweight stream ciphers have attracted significant attention in the last two decades due to their security implementations in small devices with limited hardware. With low-power computation abilities, these devices consume less power, thus reducing costs. New directions in ultra-lightweight cryptosystem design include optimizing [...] Read more.
Lightweight stream ciphers have attracted significant attention in the last two decades due to their security implementations in small devices with limited hardware. With low-power computation abilities, these devices consume less power, thus reducing costs. New directions in ultra-lightweight cryptosystem design include optimizing lightweight cryptosystems to work with a low number of gate equivalents (GEs); without affecting security, these designs consume less power via scaled-down versions of the Mutual Irregular Clocking KEYstream generator—version 2-(MICKEY 2.0) cipher. This study aims to obtain a scaled-down version of the MICKEY 2.0 cipher by modifying its internal state design via reducing shift registers and modifying the controlling bit positions to assure the ciphers’ pseudo-randomness. We measured these changes using the National Institutes of Standards and Testing (NIST) test suites, investigating the speed and power consumption of the proposed scaled-down version named MICKEY 2.0.85. The (85) refers to the new modified bit-lengths of each MICKEY 2.0 register. The results show that it is faster, requires less power, and needs fewer GEs. The proposed variant will enhance the security of applications, such asRadio-frequency identification (RFID) technology, sensor networks, and in Internet of things (IoT) in general. It also will enhance research on the optimization of existing lightweight cryptosystems. Full article
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10 pages, 3547 KiB  
Article
Super Stability of Ag Nanoparticle in Crystalline Lamellar (Lc) Liquid Crystal Matrix at Different pH Environment
by Siti Mariah Mohd Yasin, Irfan Anjum Badruddin and Mohd Rafie Johan
Symmetry 2020, 12(1), 31; https://doi.org/10.3390/sym12010031 - 22 Dec 2019
Cited by 3 | Viewed by 2982
Abstract
The symmetry concept in this paper is related to the natural self-assembly of noble metal nanoparticles in the long range periodic structure of liquid crystal (LC). The current study deliberates the effect of pH on the stability of nanoparticles (NPs) in the lamellar [...] Read more.
The symmetry concept in this paper is related to the natural self-assembly of noble metal nanoparticles in the long range periodic structure of liquid crystal (LC). The current study deliberates the effect of pH on the stability of nanoparticles (NPs) in the lamellar phase of a lyotropic LC environment. The LC was prepared by the mass ratio 0.33:0.22:0.45 for (HDTABr):1-pentanol:water. The LC containing silver nanoparticles (AgNPs) was prepared by replacing the water with Ag solution. The AgNPs were produced by the in situ preparation method in LC. The solution of AgNPs-LC was varied at different pH. The absorption intensities were determined by using ultra-violet spectroscopy (UV-vis). The surface potential and hydrodynamic particle size were determined by using Zeta-potential (measurements). The surface enhanced Raman spectroscopy (SERS) was carried out to enhance the Raman signals of 4-aminobenzenethiol (4-ABT) deposited onto AgNPs as substrate. It is found that all characterizations exhibited super stability for AgNPs dispersed in LC at pH = 3 to 12 with the optimum stability at pH = 5–6. The remarkable stability of NPs is an important indicator of the various applications in nanotechnology and nanoscience fields. Full article
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21 pages, 41741 KiB  
Article
A Novel Hybrid Data-Driven Modeling Method for Missiles
by Yongxiang He, Hongwu Guo and Yang Han
Symmetry 2020, 12(1), 30; https://doi.org/10.3390/sym12010030 - 22 Dec 2019
Cited by 4 | Viewed by 3746
Abstract
This paper proposes a novel hybrid data-driven modeling method for missiles. Based on actual flight test data, the missile hybrid model is established by combining neural networks and the mechanism modeling method, considering the uncertainties and nonlinear factors in missiles. This method can [...] Read more.
This paper proposes a novel hybrid data-driven modeling method for missiles. Based on actual flight test data, the missile hybrid model is established by combining neural networks and the mechanism modeling method, considering the uncertainties and nonlinear factors in missiles. This method can avoid the problems in missile mechanism modeling and traditional data-driven modeling, and can also provide a solution for nonlinear dynamic system modeling problems in offline usage scenarios. Finally, the feasibility of the proposed method and the credibility of the established model are verified by simulation experiments and statistical analysis. Full article
(This article belongs to the Special Issue Optimized Machine Learning Algorithms for Modeling Dynamical Systems)
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14 pages, 287 KiB  
Article
Relation-Theoretic Fixed Point Theorems for Generalized Weakly Contractive Mappings
by Priyam Chakraborty, Binayak S. Choudhury and Manuel De la Sen
Symmetry 2020, 12(1), 29; https://doi.org/10.3390/sym12010029 - 21 Dec 2019
Cited by 6 | Viewed by 2417
Abstract
In recent times there have been two prominent trends in metric fixed point theory. One is the use of weak contractive inequalities and the other is the use of binary relations. Combining the two trends, in this paper we establish a relation-theoretic fixed [...] Read more.
In recent times there have been two prominent trends in metric fixed point theory. One is the use of weak contractive inequalities and the other is the use of binary relations. Combining the two trends, in this paper we establish a relation-theoretic fixed point result for a mapping which is defined on a metric space with an arbitrary binary relation and satisfies a weak contractive inequality for any pair of points whenever the pair of points is related by a given relation. The uniqueness is obtained by assuming some extra conditions. The metric space is assumed to be R -complete. We use R -continuity of functions. The property of local T-transitivity of the relation R is used in the main theorem. There is an illustrative example. An existing fixed point result is generalized through the present work. We use a method in the proof of our main theorem which is a blending of relation-theoretic and analytic approaches. Full article
15 pages, 1898 KiB  
Article
Research on the Detection Method of Implicit Self Symmetry in a High-Level Semantic Model
by Chao Wang
Symmetry 2020, 12(1), 28; https://doi.org/10.3390/sym12010028 - 21 Dec 2019
Cited by 3 | Viewed by 2404
Abstract
In order to improve the accuracy of semantic model intrinsic detection, a skeleton-based high-level semantic model intrinsic self-symmetry detection method is proposed. The semantic analysis of the model set is realized by the uniform segmentation of the model within the same style, the [...] Read more.
In order to improve the accuracy of semantic model intrinsic detection, a skeleton-based high-level semantic model intrinsic self-symmetry detection method is proposed. The semantic analysis of the model set is realized by the uniform segmentation of the model within the same style, the component correspondence of the model between different styles, and the shape content clustering. Based on the results of clustering analysis, for a given three-dimensional (3D) point cloud model, according to the curve skeleton, the skeleton point pairs reflecting the symmetry between the model surface points are obtained by the election method, and the symmetry is extended to the model surface vertices according to these skeleton point pairs. With the help of skeleton, the symmetry of the point cloud model is obtained, and then the symmetry region of point cloud model is obtained by the symmetric correspondence matrix and spectrum method, so as to realize the intrinsic symmetry detection of the model. The experimental results show that the proposed method has the advantages of less time, high accuracy, and high reliability. Full article
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10 pages, 9647 KiB  
Article
Fully Automatic Facial Deformation Transfer
by Shaojun Bian, Anzong Zheng, Lin Gao, Greg Maguire, Willem Kokke, Jon Macey, Lihua You and Jian J. Zhang
Symmetry 2020, 12(1), 27; https://doi.org/10.3390/sym12010027 - 21 Dec 2019
Cited by 7 | Viewed by 7147
Abstract
Facial Animation is a serious and ongoing challenge for the Computer Graphic industry. Because diverse and complex emotions need to be expressed by different facial deformation and animation, copying facial deformations from existing character to another is widely needed in both industry and [...] Read more.
Facial Animation is a serious and ongoing challenge for the Computer Graphic industry. Because diverse and complex emotions need to be expressed by different facial deformation and animation, copying facial deformations from existing character to another is widely needed in both industry and academia, to reduce time-consuming and repetitive manual work of modeling to create the 3D shape sequences for every new character. But transfer of realistic facial animations between two 3D models is limited and inconvenient for general use. Modern deformation transfer methods require correspondences mapping, in most cases, which are tedious to get. In this paper, we present a fast and automatic approach to transfer the deformations of the facial mesh models by obtaining the 3D point-wise correspondences in the automatic manner. The key idea is that we could estimate the correspondences with different facial meshes using the robust facial landmark detection method by projecting the 3D model to the 2D image. Experiments show that without any manual labelling efforts, our method detects reliable correspondences faster and simpler compared with the state-of-the-art automatic deformation transfer method on the facial models. Full article
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16 pages, 4708 KiB  
Article
Skyrmion Crystals and Phase Transitions in Magneto-Ferroelectric Superlattices: Dzyaloshinskii–Moriya Interaction in a Frustrated J1J2 Model
by Ildus F. Sharafullin and Hung T. Diep
Symmetry 2020, 12(1), 26; https://doi.org/10.3390/sym12010026 - 21 Dec 2019
Cited by 14 | Viewed by 4088
Abstract
The formation of a skyrmion crystal and its phase transition are studied, taking into account the Dzyaloshinskii–Moriya (DM) interaction at the interface between a ferroelectric layer and a magnetic layer in a superlattice. Frustration is introduced in both magnetic and ferroelectric films. The [...] Read more.
The formation of a skyrmion crystal and its phase transition are studied, taking into account the Dzyaloshinskii–Moriya (DM) interaction at the interface between a ferroelectric layer and a magnetic layer in a superlattice. Frustration is introduced in both magnetic and ferroelectric films. The films have a simple cubic lattice structure. The spins inside the magnetic layers are Heisenberg spins interacting with each other via nearest-neighbor (NN) exchange J m and next-nearest-neighbor (NNN) exchange J 2 m . The polarizations in the ferroelectric layers are assumed to be of Ising type with NN and NNN interactions J f and J 2 f . At the magnetoelectric interface, a DM interaction J m f between spins and polarizations is supposed. The spin configuration in the ground state is calculated by the steepest descent method. In an applied magnetic field H perpendicular to the layers, we show that the formation of skyrmions at the magnetoelectric interface is strongly enhanced by the frustration brought about by the NNN antiferromagnetic interactions J 2 m and J 2 f . Various physical quantities at finite temperatures are obtained by Monte Carlo simulations. We show the critical temperature, the order parameters of magnetic and ferroelectric layers as functions of the interface DM coupling, the applied magnetic field, and J 2 m and J 2 f . The phase transition to the disordered phase is studied in detail. Full article
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9 pages, 308 KiB  
Article
Axion Stars
by Hong Zhang
Symmetry 2020, 12(1), 25; https://doi.org/10.3390/sym12010025 - 20 Dec 2019
Cited by 26 | Viewed by 4070
Abstract
The dark matter particle can be a QCD axion or axion-like particle. A locally over-densed distribution of axions can condense into a bound Bose–Einstein condensate called an axion star, which can be bound by self-gravity or bound by self-interactions. It is possible [...] Read more.
The dark matter particle can be a QCD axion or axion-like particle. A locally over-densed distribution of axions can condense into a bound Bose–Einstein condensate called an axion star, which can be bound by self-gravity or bound by self-interactions. It is possible that a significant fraction of the dark matter axion is in the form of axion stars. This would make some efforts searching for the axion as the dark matter particle more challenging, but at the same time it would also open up new possibilities. Some of the properties of axion stars, including their emission rates and their interactions with other astrophysical objects, are not yet completely understood. Full article
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10 pages, 392 KiB  
Article
Solitonic Fixed Point Attractors in the Complex Ginzburg–Landau Equation for Associative Memories
by Alexey N. Pyrkov, Tim Byrnes and Valentin V. Cherny
Symmetry 2020, 12(1), 24; https://doi.org/10.3390/sym12010024 - 20 Dec 2019
Cited by 3 | Viewed by 2733
Abstract
It was recently shown that the nonlinear Schrodinger equation with a simplified dissipative perturbation features a zero-velocity solitonic solution of non-zero amplitude which can be used in analogy to attractors of Hopfield’s associative memory. In this work, we consider a more complex dissipative [...] Read more.
It was recently shown that the nonlinear Schrodinger equation with a simplified dissipative perturbation features a zero-velocity solitonic solution of non-zero amplitude which can be used in analogy to attractors of Hopfield’s associative memory. In this work, we consider a more complex dissipative perturbation adding the effect of two-photon absorption and the quintic gain/loss effects that yields the complex Ginzburg–Landau equation (CGLE). We construct a perturbation theory for the CGLE with a small dissipative perturbation, define the behavior of the solitonic solutions with parameters of the system and compare the solution with numerical simulations of the CGLE. We show, in a similar way to the nonlinear Schrodinger equation with a simplified dissipation term, a zero-velocity solitonic solution of non-zero amplitude appears as an attractor for the CGLE. In this case, the amplitude and velocity of the solitonic fixed point attractor does not depend on the quintic gain/loss effects. Furthermore, the effect of two-photon absorption leads to an increase in the strength of the solitonic fixed point attractor. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
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21 pages, 3293 KiB  
Article
Creating a Computable Cognitive Model of Visual Aesthetics for Automatic Aesthetics Evaluation of Robotic Dance Poses
by Hua Peng, Jing Li, Huosheng Hu, Keli Hu, Chao Tang and Yulong Ding
Symmetry 2020, 12(1), 23; https://doi.org/10.3390/sym12010023 - 20 Dec 2019
Cited by 7 | Viewed by 3345
Abstract
Inspired by human dancers who can evaluate the aesthetics of their own dance poses through mirror observation, this paper presents a corresponding mechanism for robots to improve their cognitive and autonomous abilities. Essentially, the proposed mechanism is a brain-like intelligent system that is [...] Read more.
Inspired by human dancers who can evaluate the aesthetics of their own dance poses through mirror observation, this paper presents a corresponding mechanism for robots to improve their cognitive and autonomous abilities. Essentially, the proposed mechanism is a brain-like intelligent system that is symmetrical to the visual cognitive nervous system of the human brain. Specifically, a computable cognitive model of visual aesthetics is developed using the two important aesthetic cognitive neural models of the human brain, which is then applied in the automatic aesthetics evaluation of robotic dance poses. Three kinds of features (color, shape and orientation) are extracted in a manner similar to the visual feature elements extracted by human brains. After applying machine learning methods in different feature combinations, machine aesthetics models are built for automatic evaluation of robotic dance poses. The simulation results show that our approach can process visual information effectively by cognitive computation, and achieved a very good evaluation performance of automatic aesthetics. Full article
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12 pages, 2451 KiB  
Article
Parametric Jensen-Shannon Statistical Complexity and Its Applications on Full-Scale Compartment Fire Data
by Flavia-Corina Mitroi-Symeonidis, Ion Anghel and Nicușor Minculete
Symmetry 2020, 12(1), 22; https://doi.org/10.3390/sym12010022 - 20 Dec 2019
Cited by 8 | Viewed by 3184
Abstract
The order/disorder characteristics of a compartment fire are researched based on experimental data. From our analysis performed by new, pioneering methods, we claim that the parametric Jensen-Shannon complexity can be successfully used to detect unusual data, and that one can use it also [...] Read more.
The order/disorder characteristics of a compartment fire are researched based on experimental data. From our analysis performed by new, pioneering methods, we claim that the parametric Jensen-Shannon complexity can be successfully used to detect unusual data, and that one can use it also as a means to perform relevant analysis of fire experiments. Thoroughly comparing the performance of different algorithms (known as permutation entropy and two-length permutation entropy) to extract the probability distribution is an essential step. We discuss some of the theoretical assumptions behind each step and stress that the role of the parameter is to fine-tune the results of the Jensen-Shannon statistical complexity. Note that the Jensen-Shannon statistical complexity is symmetric, while its parametric version displays a symmetric duality due to the a priori probabilities used. Full article
(This article belongs to the Special Issue Symmetry in Applied Mathematics)
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22 pages, 1601 KiB  
Article
Emotion Classification Based on Biophysical Signals and Machine Learning Techniques
by Oana Bălan, Gabriela Moise, Livia Petrescu, Alin Moldoveanu, Marius Leordeanu and Florica Moldoveanu
Symmetry 2020, 12(1), 21; https://doi.org/10.3390/sym12010021 - 20 Dec 2019
Cited by 84 | Viewed by 11612
Abstract
Emotions constitute an indispensable component of our everyday life. They consist of conscious mental reactions towards objects or situations and are associated with various physiological, behavioral, and cognitive changes. In this paper, we propose a comparative analysis between different machine learning and deep [...] Read more.
Emotions constitute an indispensable component of our everyday life. They consist of conscious mental reactions towards objects or situations and are associated with various physiological, behavioral, and cognitive changes. In this paper, we propose a comparative analysis between different machine learning and deep learning techniques, with and without feature selection, for binarily classifying the six basic emotions, namely anger, disgust, fear, joy, sadness, and surprise, into two symmetrical categorical classes (emotion and no emotion), using the physiological recordings and subjective ratings of valence, arousal, and dominance from the DEAP (Dataset for Emotion Analysis using EEG, Physiological and Video Signals) database. The results showed that the maximum classification accuracies for each emotion were: anger: 98.02%, joy:100%, surprise: 96%, disgust: 95%, fear: 90.75%, and sadness: 90.08%. In the case of four emotions (anger, disgust, fear, and sadness), the classification accuracies were higher without feature selection. Our approach to emotion classification has future applicability in the field of affective computing, which includes all the methods used for the automatic assessment of emotions and their applications in healthcare, education, marketing, website personalization, recommender systems, video games, and social media. Full article
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24 pages, 377 KiB  
Article
Statistical Inference for the Weibull Distribution Based on δ-Record Data
by Raúl Gouet, F. Javier López, Lina Maldonado and Gerardo Sanz
Symmetry 2020, 12(1), 20; https://doi.org/10.3390/sym12010020 - 20 Dec 2019
Cited by 7 | Viewed by 3004
Abstract
We consider the maximum likelihood and Bayesian estimation of parameters and prediction of future records of the Weibull distribution from δ -record data, which consists of records and near-records. We discuss existence, consistency and numerical computation of estimators and predictors. The performance of [...] Read more.
We consider the maximum likelihood and Bayesian estimation of parameters and prediction of future records of the Weibull distribution from δ -record data, which consists of records and near-records. We discuss existence, consistency and numerical computation of estimators and predictors. The performance of the proposed methodology is assessed by Montecarlo simulations and the analysis of monthly rainfall series. Our conclusion is that inferences for the Weibull model, based on δ -record data, clearly improve inferences based solely on records. This methodology can be recommended, more so as near-records can be collected along with records, keeping essentially the same experimental design. Full article
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17 pages, 299 KiB  
Article
Bias, Precision, and Accuracy of Skewness and Kurtosis Estimators for Frequently Used Continuous Distributions
by Roser Bono, Jaume Arnau, Rafael Alarcón and Maria J. Blanca
Symmetry 2020, 12(1), 19; https://doi.org/10.3390/sym12010019 - 20 Dec 2019
Cited by 50 | Viewed by 11639
Abstract
Several measures of skewness and kurtosis were proposed by Hogg (1974) in order to reduce the bias of conventional estimators when the distribution is non-normal. Here we conducted a Monte Carlo simulation study to compare the performance of conventional and Hogg’s estimators, considering [...] Read more.
Several measures of skewness and kurtosis were proposed by Hogg (1974) in order to reduce the bias of conventional estimators when the distribution is non-normal. Here we conducted a Monte Carlo simulation study to compare the performance of conventional and Hogg’s estimators, considering the most frequent continuous distributions used in health, education, and social sciences (gamma, lognormal and exponential distributions). In order to determine the bias, precision and accuracy of the skewness and kurtosis estimators for each distribution we calculated the relative bias, the coefficient of variation, and the scaled root mean square error. The effect of sample size on the estimators is also analyzed. In addition, a SAS program for calculating both conventional and Hogg’s estimators is presented. The results indicated that for the non-normal distributions investigated, the estimators of skewness and kurtosis which best reflect the shape of the distribution are Hogg’s estimators. It should also be noted that Hogg’s estimators are not as affected by sample size as are conventional estimators. Full article
17 pages, 312 KiB  
Article
Identities and Computation Formulas for Combinatorial Numbers Including Negative Order Changhee Polynomials
by Daeyeoul Kim, Yilmaz Simsek and Ji Suk So
Symmetry 2020, 12(1), 9; https://doi.org/10.3390/sym12010009 - 19 Dec 2019
Cited by 8 | Viewed by 2444
Abstract
The purpose of this paper is to construct generating functions for negative order Changhee numbers and polynomials. Using these generating functions with their functional equation, we prove computation formulas for combinatorial numbers and polynomials. These formulas include Euler numbers and polynomials of higher [...] Read more.
The purpose of this paper is to construct generating functions for negative order Changhee numbers and polynomials. Using these generating functions with their functional equation, we prove computation formulas for combinatorial numbers and polynomials. These formulas include Euler numbers and polynomials of higher order, Stirling numbers, and negative order Changhee numbers and polynomials. We also give some properties of these numbers and polynomials with their generating functions. Moreover, we give relations among Changhee numbers and polynomials of negative order, combinatorial numbers and polynomials and Bernoulli numbers of the second kind. Finally, we give a partial derivative of an equation for generating functions for Changhee numbers and polynomials of negative order. Using these differential equations, we derive recurrence relations, differential and integral formulas for these numbers and polynomials. We also give p-adic integrals representations for negative order Changhee polynomials including Changhee numbers and Deahee numbers. Full article
14 pages, 4986 KiB  
Article
Small Wind Turbine Blade Design and Optimization
by Hani Muhsen, Wael Al-Kouz and Waqar Khan
Symmetry 2020, 12(1), 18; https://doi.org/10.3390/sym12010018 - 19 Dec 2019
Cited by 44 | Viewed by 20486
Abstract
This work aims at designing and optimizing the performance of a small Horizontal-Axis-Wind-Turbine to obtain a power coefficient (CP) higher than 40% at a low wind speed of 5 m/s. Two symmetric in shape airfoils were used to get the final [...] Read more.
This work aims at designing and optimizing the performance of a small Horizontal-Axis-Wind-Turbine to obtain a power coefficient (CP) higher than 40% at a low wind speed of 5 m/s. Two symmetric in shape airfoils were used to get the final optimized airfoil. The main objective is to optimize the blade parameters that influence the design of the blade since the small turbines are prone to show low performance due to the low Reynolds number as a result of the small size of the rotor and the low wind speed. Therefore, the optimization process will select different airfoils and extract their performance at the design conditions to find the best sections which form the optimal design of the blade. The sections of the blade in the final version mainly consist of two different sections belong to S1210 and S1223 airfoils. The optimization process goes further by investigating the performance of the final design, and it employs the blade element momentum theory to enhance the design. Finally, the rotor-design was obtained, which consists of three blades with a diameter of 4 m, a hub of 20 cm radius, a tip-speed ratio of 6.5 and can obtain about 650 W with a Power coefficient of 0.445 at a wind-speed of 5.5 m/s, reaching a power of 1.18 kW and a power coefficient of 0.40 at a wind-speed of 7 m/s. Full article
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10 pages, 8819 KiB  
Article
Complex Patterns to the (3+1)-Dimensional B-type Kadomtsev-Petviashvili-Boussinesq Equation
by Juan Luis García Guirao, H. M. Baskonus, Ajay Kumar, M. S. Rawat and Gulnur Yel
Symmetry 2020, 12(1), 17; https://doi.org/10.3390/sym12010017 - 19 Dec 2019
Cited by 38 | Viewed by 3405
Abstract
This paper presents many new complex combined dark-bright soliton solutions obtained with the help of the accurate sine-Gordon expansion method to the B-type Kadomtsev-Petviashvili-Boussinesq equation with binary power order nonlinearity. With the use of some computational programs, we plot many new surfaces of [...] Read more.
This paper presents many new complex combined dark-bright soliton solutions obtained with the help of the accurate sine-Gordon expansion method to the B-type Kadomtsev-Petviashvili-Boussinesq equation with binary power order nonlinearity. With the use of some computational programs, we plot many new surfaces of the results obtained in this paper. In addition, we present the interactions between complex travelling wave patterns and their solitons. Full article
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26 pages, 1076 KiB  
Article
Use of Nonconventional Dispersion Measures to Improve the Efficiency of Ratio-Type Estimators of Variance in the Presence of Outliers
by Farah Naz, Tahir Nawaz, Tianxiao Pang and Muhammad Abid
Symmetry 2020, 12(1), 16; https://doi.org/10.3390/sym12010016 - 19 Dec 2019
Cited by 10 | Viewed by 2173
Abstract
The use of auxiliary information in survey sampling to enhance the efficiency of the estimators of population parameters is a common phenomenon. Generally, the ratio and regression estimators are developed by using the known information on conventional parameters of the auxiliary variables, such [...] Read more.
The use of auxiliary information in survey sampling to enhance the efficiency of the estimators of population parameters is a common phenomenon. Generally, the ratio and regression estimators are developed by using the known information on conventional parameters of the auxiliary variables, such as variance, coefficient of variation, coefficient of skewness, coefficient of kurtosis, or correlation between the study and auxiliary variable. The efficiency of these estimators is dubious in the presence of outliers in the data and a nonsymmetrical population. This study presents improved variance estimators under simple random sampling without replacement with the assumption that the information on some nonconventional dispersion measures of the auxiliary variable is readily available. These auxiliary variables can be the inter-decile range, sample inter-quartile range, probability-weighted moment estimator, Gini mean difference estimator, Downton’s estimator, median absolute deviation from the median, and so forth. The algebraic expressions for the bias and mean square error of the proposed estimators are obtained and the efficiency conditions are derived to compare with the existing estimators. The percentage relative efficiencies are used to numerically compare the results of the proposed estimators with the existing estimators by using real datasets, indicating the supremacy of the suggested estimators. Full article
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8 pages, 233 KiB  
Article
A New Version of Schauder and Petryshyn Type Fixed Point Theorems in S-Modular Function Spaces
by Maryam Ramezani, Hamid Baghani, Ozgur Ege and Manuel De la Sen
Symmetry 2020, 12(1), 15; https://doi.org/10.3390/sym12010015 - 19 Dec 2019
Cited by 5 | Viewed by 1950
Abstract
In this paper, using the conditions of Taleb-Hanebaly’s theorem in a modular space where the modular is s-convex and symmetric with respect to the ordinate axis, we prove a new generalized modular version of the Schauder and Petryshyn fixed point theorems for [...] Read more.
In this paper, using the conditions of Taleb-Hanebaly’s theorem in a modular space where the modular is s-convex and symmetric with respect to the ordinate axis, we prove a new generalized modular version of the Schauder and Petryshyn fixed point theorems for nonexpansive mappings in s-convex sets. Our results can be applied to a nonlinear integral equation in Musielak-Orlicz space L p where 0 < p 1 and 0 < s p . Full article
(This article belongs to the Section Mathematics)
12 pages, 546 KiB  
Article
Particle Methods Simulations by Kinetic Theory Models of Human Crowds Accounting for Stress Conditions
by Ahmed Elaiw and Yusuf Al-Turki
Symmetry 2020, 12(1), 14; https://doi.org/10.3390/sym12010014 - 19 Dec 2019
Cited by 10 | Viewed by 3005
Abstract
This paper tackles the problem of simulating the dynamics of human crowds in high density conditions on venues which include internal obstacles and in the interaction between two crowd streams moving in two opposite directions. The role of stress condition is taken into [...] Read more.
This paper tackles the problem of simulating the dynamics of human crowds in high density conditions on venues which include internal obstacles and in the interaction between two crowd streams moving in two opposite directions. The role of stress condition is taken into account as simulations aim at providing a support to crisis managers in charge of reducing the risk of incidents. The rationale of the modeling approach is that kinetic theory approach, where individual interactions, which might be nonlinearly additive, non symmetric, and non nonlocal, lead to collective behaviors to be examined towards safety problems. Full article
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10 pages, 750 KiB  
Article
Hermite–Hadamard and Fejér Inequalities for Co-Ordinated (F,G)-Convex Functions on a Rectangle
by Małgorzata Chudziak and Marek Żołdak
Symmetry 2020, 12(1), 13; https://doi.org/10.3390/sym12010013 - 19 Dec 2019
Cited by 3 | Viewed by 2028
Abstract
We introduce the notion of a co-ordinated ( F , G ) -convex function defined on an interval in R 2 and we prove the Hermite–Hadamard and Fejér type inequalities for such functions. [...] Read more.
We introduce the notion of a co-ordinated ( F , G ) -convex function defined on an interval in R 2 and we prove the Hermite–Hadamard and Fejér type inequalities for such functions. Full article
(This article belongs to the Special Issue Symmetry in Functional Equations and Inequalities)
9 pages, 272 KiB  
Article
Fixed-Points of Interpolative Ćirić-Reich–Rus-Type Contractions in b-Metric Spaces
by Pradip Debnath and Manuel de La Sen
Symmetry 2020, 12(1), 12; https://doi.org/10.3390/sym12010012 - 19 Dec 2019
Cited by 22 | Viewed by 2762
Abstract
The concept of symmetry is inherent in the study of metric spaces due to the presence of the symmetric property of the metric. Significant results, such as with the Borsuk–Ulam theorem, make use of fixed-point arguments in their proofs to deal with certain [...] Read more.
The concept of symmetry is inherent in the study of metric spaces due to the presence of the symmetric property of the metric. Significant results, such as with the Borsuk–Ulam theorem, make use of fixed-point arguments in their proofs to deal with certain symmetry principles. As such, the study of fixed-point results in metric spaces is highly correlated with the symmetry concept. In the current paper, we first define a new and modified Ćirić-Reich–Rus-type contraction in a b-metric space by incorporating the constant s in its definition and establish the corresponding fixed-point result. Next, we adopt an interpolative approach to establish some more fixed-point theorems. Existence of fixed points for ω -interpolative Ćirić-Reich–Rus-type contractions are investigated in this context. We also illustrate the validity of our results with some examples. Full article
15 pages, 5730 KiB  
Article
Real-Time Control for the EHU Stellarator
by Izaskun Garrido, Javier Maseda, Itziar Martija and Aitor J. Garrido
Symmetry 2020, 12(1), 11; https://doi.org/10.3390/sym12010011 - 19 Dec 2019
Viewed by 2102
Abstract
At present, two main magnetic confinement fusion devices exist: tokamaks and stellarators. Moreover, stellarators have been demonstrated to be a good alternative to tokamaks, due to their ability to operate in continuous mode, which eventually translates into a higher commercial profitability. In stellarators, [...] Read more.
At present, two main magnetic confinement fusion devices exist: tokamaks and stellarators. Moreover, stellarators have been demonstrated to be a good alternative to tokamaks, due to their ability to operate in continuous mode, which eventually translates into a higher commercial profitability. In stellarators, the magnetic confinement of the plasma is achieved exclusively by the coils, thus no electric current through the plasma is needed. In particular, this article presents the Columbia Non-Neutral Torus stellarator that is located in the Automatic Control Group of Euskal Herriko Unibertsitatea (EHU). This EHU stellarator maintains symmetry in its structure due to the topology of the mesh that is formed by its coils. A cornerstone of future fusion reactors is to obtain real-time control that enables a sustained reaction. In this article, a control-oriented model for the installed magnetic confinement coils is presented. The model is based on matrices that preserve symmetry, which is defined from physical principles and then validated by different sets of experimental data. Then, based on this model, a novel predictive control suited to this particular model with symmetric objective function is implemented in the numerical simulations, and its response is compared to that of traditional controllers. Finally, this control is implemented in a real plant and the satisfactory experiment results provide validation of both the numerical model and proposed controller. Full article
(This article belongs to the Special Issue Symmetry in Nonlinear Studies)
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15 pages, 1112 KiB  
Article
Lie Symmetry Analysis of Burgers Equation and the Euler Equation on a Time Scale
by Mingshuo Liu, Huanhe Dong, Yong Fang and Yong Zhang
Symmetry 2020, 12(1), 10; https://doi.org/10.3390/sym12010010 - 19 Dec 2019
Cited by 5 | Viewed by 3288
Abstract
As a powerful tool that can be used to solve both continuous and discrete equations, the Lie symmetry analysis of dynamical systems on a time scale is investigated. Applying the method to the Burgers equation and Euler equation, we get the symmetry of [...] Read more.
As a powerful tool that can be used to solve both continuous and discrete equations, the Lie symmetry analysis of dynamical systems on a time scale is investigated. Applying the method to the Burgers equation and Euler equation, we get the symmetry of the equation and single parameter groups on a time scale. Some group invariant solutions in explicit form for the traffic flow model simulated by a Burgers equation and Euler equation with a Coriolis force on a time scale are studied. Full article
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24 pages, 919 KiB  
Article
Co-Training Semi-Supervised Deep Learning for Sentiment Classification of MOOC Forum Posts
by Jing Chen, Jun Feng, Xia Sun and Yang Liu
Symmetry 2020, 12(1), 8; https://doi.org/10.3390/sym12010008 - 18 Dec 2019
Cited by 26 | Viewed by 9216
Abstract
Sentiment classification of forum posts of massive open online courses is essential for educators to make interventions and for instructors to improve learning performance. Lacking monitoring on learners’ sentiments may lead to high dropout rates of courses. Recently, deep learning has emerged as [...] Read more.
Sentiment classification of forum posts of massive open online courses is essential for educators to make interventions and for instructors to improve learning performance. Lacking monitoring on learners’ sentiments may lead to high dropout rates of courses. Recently, deep learning has emerged as an outstanding machine learning technique for sentiment classification, which extracts complex features automatically with rich representation capabilities. However, deep neural networks always rely on a large amount of labeled data for supervised training. Constructing large-scale labeled training datasets for sentiment classification is very laborious and time consuming. To address this problem, this paper proposes a co-training, semi-supervised deep learning model for sentiment classification, leveraging limited labeled data and massive unlabeled data simultaneously to achieve performance comparable to those methods trained on massive labeled data. To satisfy the condition of two views of co-training, we encoded texts into vectors from views of word embedding and character-based embedding independently, considering words’ external and internal information. To promote the classification performance with limited data, we propose a double-check strategy sample selection method to select samples with high confidence to augment the training set iteratively. In addition, we propose a mixed loss function both considering the labeled data with asymmetric and unlabeled data. Our proposed method achieved a 89.73% average accuracy and an 93.55% average F1-score, about 2.77% and 3.2% higher than baseline methods. Experimental results demonstrate the effectiveness of the proposed model trained on limited labeled data, which performs much better than those trained on massive labeled data. Full article
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21 pages, 5130 KiB  
Article
Effects of Machine Learning Approach in Flow-Based Anomaly Detection on Software-Defined Networking
by Samrat Kumar Dey and Md. Mahbubur Rahman
Symmetry 2020, 12(1), 7; https://doi.org/10.3390/sym12010007 - 18 Dec 2019
Cited by 62 | Viewed by 7016
Abstract
Recent advancements in software-defined networking (SDN) make it possible to overcome the management challenges of traditional networks by logically centralizing the control plane and decoupling it from the forwarding plane. Through a symmetric and centralized controller, SDN can prevent security breaches, but it [...] Read more.
Recent advancements in software-defined networking (SDN) make it possible to overcome the management challenges of traditional networks by logically centralizing the control plane and decoupling it from the forwarding plane. Through a symmetric and centralized controller, SDN can prevent security breaches, but it can also bring in new threats and vulnerabilities. The central controller can be a single point of failure. Hence, flow-based anomaly detection system in OpenFlow Controller can secure SDN to a great extent. In this research, we investigated two different approaches of flow-based intrusion detection system in OpenFlow Controller. The first of which is based on machine-learning algorithm where NSL-KDD dataset with feature selection ensures the accuracy of 82% with random forest classifier using the gain ratio feature selection evaluator. In the later phase, the second approach is combined with a deep neural network (DNN)-based intrusion detection system based on gated recurrent unit-long short-term memory (GRU-LSTM) where we used a suitable ANOVA F-Test and recursive feature elimination selection method to boost classifier output and achieve an accuracy of 88%. Substantial experiments with comparative analysis clearly show that, deep learning would be a better choice for intrusion detection in OpenFlow Controller. Full article
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6 pages, 525 KiB  
Opinion
Is the Horizontal-Vertical Illusion Mainly a By-Product of Petter’s Rule?
by Alessandra Pecunioso and Christian Agrillo
Symmetry 2020, 12(1), 6; https://doi.org/10.3390/sym12010006 - 18 Dec 2019
Cited by 2 | Viewed by 5291
Abstract
The horizontal-vertical (HV) illusion is a classical example of an asymmetrical perception of size in the vertical and horizontal axes, also known as ‘anisotropy of the perceived space’. Several authors argued that the horizontally-oriented ellipse of the binocular visual field might play an [...] Read more.
The horizontal-vertical (HV) illusion is a classical example of an asymmetrical perception of size in the vertical and horizontal axes, also known as ‘anisotropy of the perceived space’. Several authors argued that the horizontally-oriented ellipse of the binocular visual field might play an important role in the emergence of this illusion. Alternatively, a length bisection bias and size-constancy mechanisms have been advocated to account for the asymmetrical perception in the two dimensions. To investigate this phenomenon, participants are commonly required to estimate the length of two separate lines, one vertical and one horizontal, often arranged in an inverted-T pattern. Here we suggest that this type of stimulus may introduce physical and subjective biases that prevent a fine investigation. In particular, we believe that Petter’s rule, that applies to two-dimensional patterns formed by two overlapping surfaces, may play a critical role that will not support an interpretation based on the shape of the binocular visual field nor a length bisection bias. Full article
(This article belongs to the Special Issue Symmetry and Asymmetry in Brain Behavior and Perception)
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15 pages, 316 KiB  
Article
Existence of Small-Energy Solutions to Nonlocal Schrödinger-Type Equations for Integrodifferential Operators in ℝN
by Jun Ik Lee, Yun-Ho Kim and Jongrak Lee
Symmetry 2020, 12(1), 5; https://doi.org/10.3390/sym12010005 - 18 Dec 2019
Cited by 2 | Viewed by 1769
Abstract
We are concerned with the following elliptic equations: ( Δ ) p , K s u + V ( x ) | u | p 2 u = λ f ( x , u ) in R N , where [...] Read more.
We are concerned with the following elliptic equations: ( Δ ) p , K s u + V ( x ) | u | p 2 u = λ f ( x , u ) in R N , where ( Δ ) p , K s is the nonlocal integrodifferential equation with 0 < s < 1 < p < + , s p < N the potential function V : R N ( 0 , ) is continuous, and f : R N × R R satisfies a Carathéodory condition. The present paper is devoted to the study of the L -bound of solutions to the above problem by employing De Giorgi’s iteration method and the localization method. Using this, we provide a sequence of infinitely many small-energy solutions whose L -norms converge to zero. The main tools were the modified functional method and the dual version of the fountain theorem, which is a generalization of the symmetric mountain-pass theorem. Full article
11 pages, 278 KiB  
Article
CQ-Type Algorithm for Reckoning Best Proximity Points of EP-Operators
by Hassan Houmani and Teodor Turcanu
Symmetry 2020, 12(1), 4; https://doi.org/10.3390/sym12010004 - 18 Dec 2019
Cited by 3 | Viewed by 2136
Abstract
We introduce a new class of non-self mappings by means of a condition which is called the (EP)-condition. This class includes proximal generalized nonexpansive mappings. It is shown that the existence of best proximity points for (EP)-mappings is equivalent to the existence of [...] Read more.
We introduce a new class of non-self mappings by means of a condition which is called the (EP)-condition. This class includes proximal generalized nonexpansive mappings. It is shown that the existence of best proximity points for (EP)-mappings is equivalent to the existence of an approximate best proximity point sequence generated by a three-step iterative process. We also construct a CQ-type algorithm which generates a strongly convergent sequence to the best proximity point for a given (EP)-mapping. Full article
(This article belongs to the Special Issue Advance in Nonlinear Analysis and Optimization)
18 pages, 1509 KiB  
Article
Efficient Edge-Cloud Publish/Subscribe Broker Overlay Networks to Support Latency-Sensitive Wide-Scale IoT Applications
by Van-Nam Pham, VanDung Nguyen, Tri D. T. Nguyen and Eui-Nam Huh
Symmetry 2020, 12(1), 3; https://doi.org/10.3390/sym12010003 - 18 Dec 2019
Cited by 12 | Viewed by 3827
Abstract
Computing services for the Internet-of-Things (IoT) play a vital role for widespread IoT deployment. A hierarchy of Edge-Cloud publish/subscribe (pub/sub) broker overlay networks that support latency-sensitive IoT applications in a scalable manner is introduced. In addition, we design algorithms to cluster edge pub/sub [...] Read more.
Computing services for the Internet-of-Things (IoT) play a vital role for widespread IoT deployment. A hierarchy of Edge-Cloud publish/subscribe (pub/sub) broker overlay networks that support latency-sensitive IoT applications in a scalable manner is introduced. In addition, we design algorithms to cluster edge pub/sub brokers based on topic similarities and geolocations to enhance data dissemination among end-to-end IoT devices. The proposed model is designed to provide low delay data dissemination and effectively save network traffic among brokers. In the proposed model, IoT devices running pub/sub client applications periodically send collected data, organized as a hierarchy of topics, to their closest edge pub/sub brokers. Then, the data are processed/analyzed at edge nodes to make controlling decisions promptly replying to the IoT devices and/or aggregated for further delivery to other interested edge brokers or to cloud brokers for long-term processing, analysis, and storage. Extensive simulation results demonstrate that our proposal achieves the best data delivery latency compared to two baseline schemes, a classical Cloud-based pub/sub scheme and an Edge-Cloud pub/sub scheme. Considering the similar Edge-Cloud technique, the proposed scheme outperforms PubSubCoord-alike in terms of relay traffic ratio among brokers. Therefore, our proposal can adapt well to support wide-scale latency-sensitive IoT applications. Full article
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10 pages, 644 KiB  
Article
A Structured Table of Graphs with Symmetries and Other Special Properties
by Yidan Zhang, Xiaolong Huang, Zhipeng Xu and Yuefan Deng
Symmetry 2020, 12(1), 2; https://doi.org/10.3390/sym12010002 - 18 Dec 2019
Cited by 3 | Viewed by 2787
Abstract
We organize a table of regular graphs with minimal diameters and minimal mean path lengths, large bisection widths and high degrees of symmetries, obtained by enumerations on supercomputers. These optimal graphs, many of which are newly discovered, may find wide applications, for example, [...] Read more.
We organize a table of regular graphs with minimal diameters and minimal mean path lengths, large bisection widths and high degrees of symmetries, obtained by enumerations on supercomputers. These optimal graphs, many of which are newly discovered, may find wide applications, for example, in design of network topologies. Full article
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24 pages, 8883 KiB  
Article
A Balance Interface Design and Instant Image-based Traffic Assistant Agent Based on GPS and Linked Open Data Technology
by Fu-Hsien Chen and Sheng-Yuan Yang
Symmetry 2020, 12(1), 1; https://doi.org/10.3390/sym12010001 - 18 Dec 2019
Cited by 18 | Viewed by 3881
Abstract
Taiwan is a highly informational country, and a robust traffic network is not only critical to the national economy, but is also an important infrastructure for economic development. This paper aims to integrate government open data and global positioning system (GPS) technology to [...] Read more.
Taiwan is a highly informational country, and a robust traffic network is not only critical to the national economy, but is also an important infrastructure for economic development. This paper aims to integrate government open data and global positioning system (GPS) technology to build an instant image-based traffic assistant agent with user-friendly interfaces, thus providing more convenient real-time traffic information for users and relevant government units. The proposed system is expected to overcome the difficulty of accurately distinguishing traffic information and to solve the problem of some road sections not providing instant information. Taking the New Taipei City Government traffic open data as an example, the proposed system can display information pages at an optimal size on smartphones and other computer devices, and integrate database analysis to instantly view traffic information. Users can enter the system without downloading the application and can access the cross-platform services using device browsers. The proposed system also provides a user reporting mechanism, which informs vehicle drivers on congested road sections about road conditions. Comparison and analysis of the system with similar applications shows that although they have similar functions, the proposed system offers more practicability, better information accessibility, excellent user experience, and approximately the optimal balance (a kind of symmetry) of the important items of the interface design. Full article
(This article belongs to the Special Issue Selected Papers from IIKII 2019 conferences in Symmetry)
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