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Volume 11, December

Symmetry, Volume 12, Issue 1 (January 2020) – 184 articles

Cover Story (view full-size image): Topological spin textures known as skyrmions have been discovered in various materials. They were immediately utilized in numerous industrial applications in various domains, from electronic transport to skyrmion-based racetrack memory and skyrmion-based transistor. Theoretical models and numerical simulations have been proposed to explain the fascinating properties of skyrmions. View this paper.
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Open AccessArticle
Bilateral and Unilateral Asymmetries of Strength and Flexibility in Young Elite Sailors: Windsurfing, Optimist and Laser Classes
Symmetry 2020, 12(1), 184; https://doi.org/10.3390/sym12010184 - 20 Jan 2020
Cited by 3 | Viewed by 1155
Abstract
In sport sailing, performance is related to the sailor’s ability to maintain the stability of the boat, and the boat class determines the variables involved in such ability. In monohull-type vessels, such as the Optimist and Laser classes, the flexibility of the hip [...] Read more.
In sport sailing, performance is related to the sailor’s ability to maintain the stability of the boat, and the boat class determines the variables involved in such ability. In monohull-type vessels, such as the Optimist and Laser classes, the flexibility of the hip joint is a key performance factor. In the Windsurfing class, performance is determined by the strength of the flexors of the fingers and elbows. The performance of the sailor may be affected by asymmetries in the strength and flexibility of the muscles and joints involved in technical actions. The objective of this study was to evaluate asymmetries in strength and flexibility in young sailors. Thirty-three young sailors (ten girls) from the Windsurfing, Optimist and Laser classes were assessed for manual strength and flexibility, by dynamometry and straight leg lift tests, respectively. The symmetry index and the functional asymmetry of compression force were calculated. The results showed no differences between sailors according to gender. The sailors of the Laser class obtained the highest levels of manual strength, whereas those of the Windsurfing class showed the highest flexibility levels. The girls’ group and Windsurfing class had the highest percentage of sailors with strength asymmetry, whereas, the sailors of the Optimist class presented a greater percentage of asymmetry in flexibility. There were no differences in upper limb strength and lower limb flexibility between the dominant and non-dominant sides. Full article
(This article belongs to the Special Issue Applications Based on Symmetrical Characteristics of the Human Body)
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Open AccessArticle
Relativistic Gravitation Based on Symmetry
Symmetry 2020, 12(1), 183; https://doi.org/10.3390/sym12010183 - 20 Jan 2020
Cited by 2 | Viewed by 907
Abstract
We present a Relativistic Newtonian Dynamics ( R N D ) for motion of objects in a gravitational field generated by a moving source. As in General Relativity ( G R ), we assume that objects move by a geodesic with respect to [...] Read more.
We present a Relativistic Newtonian Dynamics ( R N D ) for motion of objects in a gravitational field generated by a moving source. As in General Relativity ( G R ), we assume that objects move by a geodesic with respect to some metric, which is defined by the field. This metric is defined on flat lab spacetime and is derived using only symmetry, the fact that the field propagates with the speed of light, and the Newtonian limit. For a field of a single source, the influenced direction of the field at spacetime point x is defined as the direction from x to the to the position of the source at the retarded time. The metric depends only on this direction and the strength of the field at x. We show that for a static source, the R N D metric is of the same form as the Whitehead metric, and the Schwarzschild metric in Eddington–Finkelstein coordinates. Motion predicted under this model passes all classical tests of G R . Moreover, in this model, the total time for a round trip of light is as predicted by G R , but velocities of light and object and time dilation differ from the G R predictions. For example, light rays propagating toward the massive object do not slow down. The new time dilation prediction could be observed by measuring the relativistic redshift for stars near a black hole and for sungrazing comets. Terrestrial experiments to test speed of light predictions and the relativistic redshift are proposed. The R N D model is similar to Whitehead’s gravitation model for a static field, but its proposed extension to the non-static case is different. This extension uses a complex four-potential description of fields propagating with the speed of light. Full article
(This article belongs to the Special Issue Relativity Based on Symmetry)
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Open AccessArticle
A Method of L1-Norm Principal Component Analysis for Functional Data
Symmetry 2020, 12(1), 182; https://doi.org/10.3390/sym12010182 - 20 Jan 2020
Viewed by 852
Abstract
Recently, with the popularization of intelligent terminals, research on intelligent big data has been paid more attention. Among these data, a kind of intelligent big data with functional characteristics, which is called functional data, has attracted attention. Functional data principal component analysis (FPCA), [...] Read more.
Recently, with the popularization of intelligent terminals, research on intelligent big data has been paid more attention. Among these data, a kind of intelligent big data with functional characteristics, which is called functional data, has attracted attention. Functional data principal component analysis (FPCA), as an unsupervised machine learning method, plays a vital role in the analysis of functional data. FPCA is the primary step for functional data exploration, and the reliability of FPCA plays an important role in subsequent analysis. However, classical L2-norm functional data principal component analysis (L2-norm FPCA) is sensitive to outliers. Inspired by the multivariate data L1-norm principal component analysis methods, we propose an L1-norm functional data principal component analysis method (L1-norm FPCA). Because the proposed method utilizes L1-norm, the L1-norm FPCs are less sensitive to the outliers than L2-norm FPCs which are the characteristic functions of symmetric covariance operator. A corresponding algorithm for solving the L1-norm maximized optimization model is extended to functional data based on the idea of the multivariate data L1-norm principal component analysis method. Numerical experiments show that L1-norm FPCA proposed in this paper has a better robustness than L2-norm FPCA, and the reconstruction ability of the L1-norm principal component analysis to the original uncontaminated functional data is as good as that of the L2-norm principal component analysis. Full article
(This article belongs to the Special Issue Novel Machine Learning Approaches for Intelligent Big Data 2019)
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Open AccessArticle
Problems of Creation and Usage of 3D Model of Structures and Theirs Possible Solution
Symmetry 2020, 12(1), 181; https://doi.org/10.3390/sym12010181 - 20 Jan 2020
Cited by 2 | Viewed by 770
Abstract
This article describes problems that occur when creating three-dimensional (3D) building models. The first problem is geometric accuracy; the next is the quality of visualization of the resulting model. The main cause of this situation is that current Computer-Aided Design (CAD) software does [...] Read more.
This article describes problems that occur when creating three-dimensional (3D) building models. The first problem is geometric accuracy; the next is the quality of visualization of the resulting model. The main cause of this situation is that current Computer-Aided Design (CAD) software does not have sufficient means to precision mapping the measured data of a given object in field. Therefore the process of 3D model creation is mainly a relatively high proportion of manual work when connecting individual points, approximating curves and surfaces, or laying textures on surfaces. In some cases, it is necessary to generalize the model in the CAD system, which degrades the accuracy and quality of field data. The article analyzes these problems and then recommends several variants for their solution. There are described two basic methods: using topological codes in the list of coordinates points and creating new special CAD features while using Python scripts. These problems are demonstrated on examples of 3D models in practice. These are mainly historical buildings in different locations and different designs (brick or wooden structures). These are four sacral buildings in the Czech Republic (CR): the church of saints Johns of Brno-Bystrc, the Church of St. Paraskiva in Blansko, further the Strejc’s Church in Židlochovice, and Church of St. Peter in Alcantara in Karviná city. All of the buildings were geodetically surveyed by terrestrial method while using total station. The 3D model was created in both cases in the program AUTOCAD v. 18 and MicroStation. Full article
(This article belongs to the Special Issue Selected Papers from IIKII 2019 conferences in Symmetry)
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Open AccessArticle
Particular Solutions of Ordinary Differential Equations Using Discrete Symmetry Groups
Symmetry 2020, 12(1), 180; https://doi.org/10.3390/sym12010180 - 19 Jan 2020
Cited by 1 | Viewed by 628
Abstract
This article explains how discrete symmetry groups can be directly applied to obtain the particular solutions of nonlinear ordinary differential equations (ODEs). The particular solutions of some nonlinear ordinary differential equations have been generated by means of their discrete symmetry groups. Full article
(This article belongs to the Special Issue Ordinary and Partial Differential Equations: Theory and Application)
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Open AccessArticle
A Novel Surface Inset Permanent Magnet Synchronous Motor for Electric Vehicles
Symmetry 2020, 12(1), 179; https://doi.org/10.3390/sym12010179 - 19 Jan 2020
Cited by 2 | Viewed by 736
Abstract
Aiming to successfully meet the requirements of a large output torque and a wide range of flux weakening speed expansion in permanent magnet synchronous motors (PMSM) for electric vehicles, a novel surface insert permanent magnet synchronous motor (SIPMSM) is developed. The method of [...] Read more.
Aiming to successfully meet the requirements of a large output torque and a wide range of flux weakening speed expansion in permanent magnet synchronous motors (PMSM) for electric vehicles, a novel surface insert permanent magnet synchronous motor (SIPMSM) is developed. The method of notching auxiliary slots between the magnetic poles in the rotor and unequal thickness magnetic poles is proposed to improve the performance of the motor. By analyzing the magnetic circuit characteristics of the novel SIPMSM, the notching auxiliary slots between the adjacent magnetic poles can affect the q-axis inductance, and the shape of magnetic pole effects the d-axis inductance of the motor. The combined action of the two factors not only weakens the cogging torque, but also improves the flux weakening capability of the motor. In this paper, the response surface methodology (RSM) is used to establish a mathematical model of the relationship between the structural parameters of the motor and the optimization objectives, and the optimal design of the motor is completed by solving the mathematical model. Experimental validation has been conducted to show the correctness and effectiveness of the proposed SIPMSM. Full article
(This article belongs to the Special Issue Symmetry in Mechanical Engineering)
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Open AccessArticle
Symmetry Group Classification and Conservation Laws of the Nonlinear Fractional Diffusion Equation with the Riesz Potential
Symmetry 2020, 12(1), 178; https://doi.org/10.3390/sym12010178 - 19 Jan 2020
Cited by 1 | Viewed by 603
Abstract
Symmetry properties of a nonlinear two-dimensional space-fractional diffusion equation with the Riesz potential of the order α ( 0 , 1 ) are studied. Lie point symmetry group classification of this equation is performed with respect to diffusivity function. To construct conservation [...] Read more.
Symmetry properties of a nonlinear two-dimensional space-fractional diffusion equation with the Riesz potential of the order α ( 0 , 1 ) are studied. Lie point symmetry group classification of this equation is performed with respect to diffusivity function. To construct conservation laws for the considered equation, the concept of nonlinear self-adjointness is adopted to a certain class of space-fractional differential equations with the Riesz potential. It is proved that the equation in question is nonlinearly self-adjoint. An extension of Ibragimov’s constructive algorithm for finding conservation laws is proposed, and the corresponding Noether operators for fractional differential equations with the Riesz potential are presented in an explicit form. To illustrate the proposed approach, conservation laws for the considered nonlinear space-fractional diffusion equation are constructed by using its Lie point symmetries. Full article
Open AccessArticle
Critically-Finite Dynamics on the Icosahedron
Symmetry 2020, 12(1), 177; https://doi.org/10.3390/sym12010177 - 19 Jan 2020
Viewed by 688
Abstract
A recent effort used two rational maps on the Riemann sphere to produce polyhedral structures with properties exemplified by a soccer ball. A key feature of these maps is their respect for the rotational symmetries of the icosahedron. The present article shows how [...] Read more.
A recent effort used two rational maps on the Riemann sphere to produce polyhedral structures with properties exemplified by a soccer ball. A key feature of these maps is their respect for the rotational symmetries of the icosahedron. The present article shows how to build such “dynamical polyhedra” for other icosahedral maps. First, algebra associated with the icosahedron determines a special family of maps with 60 periodic critical points. The topological behavior of each map is then worked out and results in a geometric algorithm out of which emerges a system of edges—the dynamical polyhedron—in natural correspondence to a map’s topology. It does so in a procedure that is more robust than the earlier implementation. The descriptions of the maps’ geometric behavior fall into combinatorial classes the presentation of which concludes the paper. Full article
(This article belongs to the Special Issue Symmetry and Dynamical Systems)
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Open AccessArticle
Soliton Solutions of Mathematical Physics Models Using the Exponential Function Technique
Symmetry 2020, 12(1), 176; https://doi.org/10.3390/sym12010176 - 19 Jan 2020
Cited by 1 | Viewed by 920
Abstract
This paper is based on finding the exact solutions for Burger’s equation, Zakharov-Kuznetsov (ZK) equation and Kortewegde vries (KdV) equation by utilizing exponential function method that depends on the series of exponential functions. The exponential function method utilizes the homogeneous balancing principle to [...] Read more.
This paper is based on finding the exact solutions for Burger’s equation, Zakharov-Kuznetsov (ZK) equation and Kortewegde vries (KdV) equation by utilizing exponential function method that depends on the series of exponential functions. The exponential function method utilizes the homogeneous balancing principle to find the solutions of nonlinear equations. This method is simple, wide-reaching and helpful for finding the exact solution of nonlinear conformable PDEs. Full article
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Open AccessArticle
Relation of Superconducting Pairing Symmetry and Non-Magnetic Impurity Effects in Vortex States
Symmetry 2020, 12(1), 175; https://doi.org/10.3390/sym12010175 - 18 Jan 2020
Cited by 1 | Viewed by 719
Abstract
Non-magnetic impurity scattering effects on the vortex core states are theoretically studied to clarify the contributions from the sign-change of the pairing function in anisotropic superconductors. The vortex states are calculated by the Eilenberger theory in superconductors with p x -wave pairing symmetry, [...] Read more.
Non-magnetic impurity scattering effects on the vortex core states are theoretically studied to clarify the contributions from the sign-change of the pairing function in anisotropic superconductors. The vortex states are calculated by the Eilenberger theory in superconductors with p x -wave pairing symmetry, as well as the corresponding anisotropic s-wave symmetry. From the spatial structure of the pair potential and the local electronic states around a vortex, we examine the differences between anisotropic superconductors with and without sign-change of the pairing function, and estimate how twofold symmetric vortex core images change with increasing the impurity scattering rate both in the Born and the unitary limits. We found that twofold symmetric vortex core image of zero-energy local density of states changes the orientation of the twofold symmetry with increasing the scattering rate when the sign change occurs in the pairing function. Without the sign change, the vortex core shape reduces to circular one with approaching dirty cases. These results of the impurity effects are valuable for identifying the pairing symmetry by observation of the vortex core image by the STM observation. Full article
(This article belongs to the Special Issue Vortex, Topology and Singularity in Quantum Systems)
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Open AccessArticle
Modulational Instability, Inter-Component Asymmetry, and Formation of Quantum Droplets in One-Dimensional Binary Bose Gases
Symmetry 2020, 12(1), 174; https://doi.org/10.3390/sym12010174 - 18 Jan 2020
Cited by 10 | Viewed by 950
Abstract
Quantum droplets are ultradilute liquid states that emerge from the competitive interplay of two Hamiltonian terms, the mean-field energy and beyond-mean-field correction, in a weakly interacting binary Bose gas. We relate the formation of droplets in symmetric and asymmetric two-component one-dimensional boson systems [...] Read more.
Quantum droplets are ultradilute liquid states that emerge from the competitive interplay of two Hamiltonian terms, the mean-field energy and beyond-mean-field correction, in a weakly interacting binary Bose gas. We relate the formation of droplets in symmetric and asymmetric two-component one-dimensional boson systems to the modulational instability of a spatially uniform state driven by the beyond-mean-field term. Asymmetry between the components may be caused by their unequal populations or unequal intra-component interaction strengths. Stability of both symmetric and asymmetric droplets is investigated. Robustness of the symmetric solutions against symmetry-breaking perturbations is confirmed. Full article
(This article belongs to the Special Issue Symmetry and Mesoscopic Physics)
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Open AccessArticle
Average Run Length on CUSUM Control Chart for Seasonal and Non-Seasonal Moving Average Processes with Exogenous Variables
Symmetry 2020, 12(1), 173; https://doi.org/10.3390/sym12010173 - 16 Jan 2020
Viewed by 660
Abstract
The aim of this study was to derive explicit formulas of the average run length (ARL) of a cumulative sum (CUSUM) control chart for seasonal and non-seasonal moving average processes with exogenous variables, and then evaluate it against the numerical integral equation (NIE) [...] Read more.
The aim of this study was to derive explicit formulas of the average run length (ARL) of a cumulative sum (CUSUM) control chart for seasonal and non-seasonal moving average processes with exogenous variables, and then evaluate it against the numerical integral equation (NIE) method. Both methods had similarly excellent agreement, with an absolute percentage error of less than 0.50%. When compared to other methods, the explicit formula method is extremely useful for finding optimal parameters when other methods cannot. In this work, the procedure for obtaining optimal parameters—which are the reference value ( a ) and control limit ( h )—for designing a CUSUM chart with a minimum out-of-control ARL is presented. In addition, the explicit formulas for the CUSUM control chart were applied with the practical data of a stock price from the stock exchange of Thailand, and the resulting performance efficiency is compared with an exponentially weighted moving average (EWMA) control chart. This comparison showed that the CUSUM control chart efficiently detected a small shift size in the process, whereas the EWMA control chart was more efficient for moderate to large shift sizes. Full article
Open AccessArticle
Limited Non-Preemptive EDF Scheduling for a Real-Time System with Symmetry Multiprocessors
Symmetry 2020, 12(1), 172; https://doi.org/10.3390/sym12010172 - 16 Jan 2020
Cited by 2 | Viewed by 653
Abstract
In a real-time system, a series of jobs invoked by each task should finish its execution before its deadline, and EDF (Earliest Deadline First) is one of the most popular scheduling algorithms to meet such timing constraints of a set of given tasks. [...] Read more.
In a real-time system, a series of jobs invoked by each task should finish its execution before its deadline, and EDF (Earliest Deadline First) is one of the most popular scheduling algorithms to meet such timing constraints of a set of given tasks. However, EDF is known to be ineffective in meeting timing constraints for non-preemptive tasks (which disallow any preemption) when the system does not know the future job release patterns of the tasks. In this paper, we develop a scheduling algorithm for a real-time system with a symmetry multiprocessor platform, which requires only limited information about the future job release patterns of a set of non-preemptive tasks, called LCEDF. We then derive its schedulability analysis that provides timing guarantees of the non-preemptive task set on a symmetry multiprocessor platform. Via simulations, we demonstrate the proposed schedulability analysis for LCEDF significantly improves the schedulability performance in meeting timing constraints of a set of non-preemptive tasks up to 20.16%, compared to vanilla non-preemptive EDF. Full article
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Open AccessArticle
w-b-Cone Distance and Its Related Results: A Survey
Symmetry 2020, 12(1), 171; https://doi.org/10.3390/sym12010171 - 16 Jan 2020
Cited by 3 | Viewed by 550
Abstract
In this work, we define the concept of a w-b-cone distance in t v s -cone b-metric spaces which differs from generalized c-distance in cone b-metric spaces, and we discuss its properties. Our results are significant, since [...] Read more.
In this work, we define the concept of a w-b-cone distance in t v s -cone b-metric spaces which differs from generalized c-distance in cone b-metric spaces, and we discuss its properties. Our results are significant, since all of the results in fixed point theory with respect to a generalized c-distance can be introduced in the version of w-b-cone distance. Moreover, using Minkowski functionals in topological vector spaces, we prove the equivalence between some fixed point results with respect to a w t -distance in general b-metric spaces and a w-b-cone distance in t v s -cone b-metric spaces. Full article
(This article belongs to the Special Issue Nonlinear, Convex, Nonsmooth, Functional Analysis in Symmetry)
Open AccessArticle
Lie Symmetry Analysis, Explicit Solutions and Conservation Laws of a Spatially Two-Dimensional Burgers–Huxley Equation
Symmetry 2020, 12(1), 170; https://doi.org/10.3390/sym12010170 - 16 Jan 2020
Cited by 10 | Viewed by 922
Abstract
In this paper, we investigate a spatially two-dimensional Burgers–Huxley equation that depicts the interaction between convection effects, diffusion transport, reaction gadget, nerve proliferation in neurophysics, as well as motion in liquid crystals. We have used the Lie symmetry method to study the vector [...] Read more.
In this paper, we investigate a spatially two-dimensional Burgers–Huxley equation that depicts the interaction between convection effects, diffusion transport, reaction gadget, nerve proliferation in neurophysics, as well as motion in liquid crystals. We have used the Lie symmetry method to study the vector fields, optimal systems of first order, symmetry reductions, and exact solutions. Furthermore, using the power series method, a set of series solutions are obtained. Finally, conservation laws are derived using optimal systems. Full article
Open AccessArticle
The Generalized Distance Spectrum of the Join of Graphs
Symmetry 2020, 12(1), 169; https://doi.org/10.3390/sym12010169 - 15 Jan 2020
Cited by 3 | Viewed by 691
Abstract
Let G be a simple connected graph. In this paper, we study the spectral properties of the generalized distance matrix of graphs, the convex combination of the symmetric distance matrix D ( G ) and diagonal matrix of the vertex transmissions T r [...] Read more.
Let G be a simple connected graph. In this paper, we study the spectral properties of the generalized distance matrix of graphs, the convex combination of the symmetric distance matrix D ( G ) and diagonal matrix of the vertex transmissions T r ( G ) . We determine the spectrum of the join of two graphs and of the join of a regular graph with another graph, which is the union of two different regular graphs. Moreover, thanks to the symmetry of the matrices involved, we study the generalized distance spectrum of the graphs obtained by generalization of the join graph operation through their eigenvalues of adjacency matrices and some auxiliary matrices. Full article
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Open AccessArticle
On Hypergroups with a β-Class of Finite Height
Symmetry 2020, 12(1), 168; https://doi.org/10.3390/sym12010168 - 15 Jan 2020
Cited by 3 | Viewed by 479
Abstract
In every hypergroup, the equivalence classes modulo the fundamental relation β are the union of hyperproducts of element pairs. Making use of this property, we introduce the notion of height of a β -class and we analyze properties of hypergroups where the height [...] Read more.
In every hypergroup, the equivalence classes modulo the fundamental relation β are the union of hyperproducts of element pairs. Making use of this property, we introduce the notion of height of a β -class and we analyze properties of hypergroups where the height of a β -class coincides with its cardinality. As a consequence, we obtain a new characterization of 1-hypergroups. Moreover, we define a hierarchy of classes of hypergroups where at least one β -class has height 1 or cardinality 1, and we enumerate the elements in each class when the size of the hypergroups is n 4 , apart from isomorphisms. Full article
Open AccessArticle
A Novel Isomap-SVR Soft Sensor Model and Its Application in Rotary Kiln Calcination Zone Temperature Prediction
Symmetry 2020, 12(1), 167; https://doi.org/10.3390/sym12010167 - 14 Jan 2020
Cited by 1 | Viewed by 594
Abstract
Soft sensing technology has been proved to be an effective tool for the online estimation of unmeasured or variables that are difficult to directly measure. The performance of a soft sensor depends heavily on its convergence speed and generalization ability to a great [...] Read more.
Soft sensing technology has been proved to be an effective tool for the online estimation of unmeasured or variables that are difficult to directly measure. The performance of a soft sensor depends heavily on its convergence speed and generalization ability to a great extent. Based on this idea, we propose a new soft sensor model, Isomap-SVR. First, the sample data set is divided into training set and testing set by using self-organizing map (SOM) neural network to ensure the fairness and symmetry of data segmentation. Isometric feature mapping (Isomap) method is used for dimensionality reduction of the model input data, which could not only reduce the structure complexity of the proposed model but speed up learning speed, and then the Support Vector Machine Regression (SVR) is applied to the regression model. A novel bat algorithm based on Cauchy mutation and Lévy flight strategy is used to optimize parameters of Isomap and SVR to improve the accuracy of the proposed model. Finally, the model is applied to the prediction of the temperature of rotary kiln calcination zone, which is difficult to measure directly. The simulation results show that the proposed soft sensor modeling method has higher learning speed and better generalization ability. Compared with other algorithms, this algorithm has obvious advantages and is an effective modeling method. Full article
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Open AccessArticle
Efficient Lattice CP-ABE AC Scheme Supporting Reduced-OBDD Structure for CCN/NDN
Symmetry 2020, 12(1), 166; https://doi.org/10.3390/sym12010166 - 14 Jan 2020
Viewed by 634
Abstract
In line with the proposed 5th Generation network, content centric network/named data networking (CCN/NDN) has been offered as one of the promising paradigms to cope with the communication needs of future realistic network communications. CCN/NDN allows network communication based on content names and [...] Read more.
In line with the proposed 5th Generation network, content centric network/named data networking (CCN/NDN) has been offered as one of the promising paradigms to cope with the communication needs of future realistic network communications. CCN/NDN allows network communication based on content names and also allows users to obtain information from any of the nearest intermediary caches on the network. Due to that, the ability of cached content to protect itself is essential since contents can be cached on any node everywhere, and publishers may not have total control over their own published data. The attribute based encryption (ABE) scheme is a preferable approach, identified to enable cached contents to be self-secured since it has a special property of encryption with policies. However, most of the proposed ABE schemes for CCN/NDN suffer from some loopholes. They are not flexible in the expression of access policy, they are inefficient, they are based on bilinear maps with pairings, and they are vulnerable to quantum cryptography algorithms. Hence, we propose the ciphertext policy attribute based encryption access control (CP-ABE AC) scheme from a lightweight ideal lattice based on ring learning with error (R-LWE) problem, and demonstrated its use in practical applications. The proposed scheme is proved to be secure and efficient under the decision ring LWE problem in the selective set model. To achieve an efficient scheme, we used an efficient trapdoor technique and the access tree representation of access structure describing the access policies was modified into a new structure, based on a reduced ordered binary decision diagram (reduce-OBDD). This access structure can support Boolean operations such as AND, NOT, OR, and threshold gates. The final result showed that the proposed scheme was secure and efficient for applications, thereby supporting CCN/NDN as a promising paradigm. Full article
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Open AccessArticle
A 12-bit 30 MS/s Successive Approximation-Register Analog-to-Digital Converter with Foreground Digital Calibration Algorithm
Symmetry 2020, 12(1), 165; https://doi.org/10.3390/sym12010165 - 14 Jan 2020
Viewed by 598
Abstract
This paper presents a foreground digital calibration algorithm based on a dynamic comparator that aims to reduce comparator offset and capacitor mismatch, as well as improve the performance of the successive approximation analog-to-digital converter (SARADC). The dynamic comparator is designed with two preamplifiers [...] Read more.
This paper presents a foreground digital calibration algorithm based on a dynamic comparator that aims to reduce comparator offset and capacitor mismatch, as well as improve the performance of the successive approximation analog-to-digital converter (SARADC). The dynamic comparator is designed with two preamplifiers and one latch to facilitate high speed, high precision, and low noise. The foreground digital calibration algorithm provides high speed with minimal area consumption. This design is implemented on a 12-bit 30 MS/s SARADC with a standard 0.13 μm Complementary Metal Oxide Semiconductor (CMOS) process. The simulation Nyquist 68.56 dB signal-to-noise-and-distortion ratio (SNDR) and 84.45 dBc spurious free dynamic range (SFDR) at 30 MS/s, differential nonlinearity (DNL) and integral nonlinearity (INL) are within 0.64 Least Significant Bits (LSB) and 1.3 LSB, respectively. The ADC achieves an effective number of bits (ENOB) of 11.08 and a figure-of-merit (FoM) of 39.45 fJ/conv.-step. Full article
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Open AccessArticle
A Novel Integrated Subjective-Objective MCDM Model for Alternative Ranking in Order to Achieve Business Excellence and Sustainability
Symmetry 2020, 12(1), 164; https://doi.org/10.3390/sym12010164 - 14 Jan 2020
Cited by 6 | Viewed by 899
Abstract
Achieving sustainability in constant development in every area in today’s modern business has become a challenge on the one hand, and an imperative on the other. If the aspect of business excellence achievement is also added to it, the complexity of the system [...] Read more.
Achieving sustainability in constant development in every area in today’s modern business has become a challenge on the one hand, and an imperative on the other. If the aspect of business excellence achievement is also added to it, the complexity of the system increases significantly, and it is necessary to model a system considering several parameters and satisfying the multi-criteria function. This paper develops a novel integrated model that involves the application of a subjective-objective model in order to achieve business sustainability and excellence. The model consists of fuzzy PIPRECIA (fuzzy pivot pairwise relative criteria importance Assessment) as a subjective method, CRITIC (criteria importance through intercriteria correlation) and I-distance method as objective methods. The goal is to take the advantages of these approaches and allow for more accurate and balanced (symmetric) decision-making through their integration. The integrated subjective-objective model has been applied in a narrow geographical area to consider and evaluate banks as a significant factor in improving the social aspect of sustainability. An additional contribution of the paper is a critical overview of multi-criteria problems in which the levels of the hierarchical structure contain a different (asymmetric) number of elements. A specific example has also been used to prove that only a hierarchical structure with an equal number of lower-level elements provides precise weights of criteria in accordance with the preferences of decision-makers referring to subjective models. The results obtained are verified throughout the calculation of Spearman and Pearson correlation coefficients, and throughout a sensitivity analysis involving a dynamic reverse rank matrix. Full article
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Open AccessArticle
On Neutrosophic Extended Triplet LA-hypergroups and Strong Pure LA-semihypergroups
Symmetry 2020, 12(1), 163; https://doi.org/10.3390/sym12010163 - 14 Jan 2020
Cited by 1 | Viewed by 524
Abstract
We introduce the notions of neutrosophic extended triplet LA-semihypergroup, neutrosophic extended triplet LA-hypergroup, which can reflect some symmetry of hyperoperation and discuss the relationships among them and regular LA-semihypergroups, LA-hypergroups, regular LA-hypergroups. In particular, we introduce the notion of strong pure neutrosophic extended [...] Read more.
We introduce the notions of neutrosophic extended triplet LA-semihypergroup, neutrosophic extended triplet LA-hypergroup, which can reflect some symmetry of hyperoperation and discuss the relationships among them and regular LA-semihypergroups, LA-hypergroups, regular LA-hypergroups. In particular, we introduce the notion of strong pure neutrosophic extended triplet LA-semihypergroup, get some special properties of it and prove the construction theorem about it under the condition of asymmetry. The examples in this paper are all from Python programs. Full article
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Open AccessFeature PaperArticle
Modelling of Autonomous Search and Rescue Missions by Interval-Valued Neutrosophic WASPAS Framework
Symmetry 2020, 12(1), 162; https://doi.org/10.3390/sym12010162 - 13 Jan 2020
Cited by 4 | Viewed by 802
Abstract
The application of autonomous robots in search and rescue missions represents a complex task which requires a robot to make robust decisions in unknown and dangerous environments. However, imprecise robot movements and small measurement errors obtained by robot sensors can have an impact [...] Read more.
The application of autonomous robots in search and rescue missions represents a complex task which requires a robot to make robust decisions in unknown and dangerous environments. However, imprecise robot movements and small measurement errors obtained by robot sensors can have an impact on the autonomous environment exploration quality, and therefore, should be addressed while designing search and rescue (SAR) robots. In this paper, a novel frontier evaluation strategy is proposed, that address technical, economic, social, and environmental factors of the sustainable environment exploration process, and a new extension of the weighted aggregated sum product assessment (WASPAS) method, modelled under interval-valued neutrosophic sets (IVNS), is introduced for autonomous mobile robots. The general-purpose Pioneer 3-AT robot platform is applied in simulated search and rescue missions, and the conducted experimental assessment shows the proposed method efficiency in commercial and public-type building exploration. By addressing the estimated measurement errors in the initial data obtained by the robot sensors, the proposed decision-making framework provides additional reliability for comparing and ranking candidate frontiers. The interval-valued multi-criteria decision-making method combined with the proposed frontier evaluation strategy enables the robot to exhaustively explore and map smaller SAR mission environments as well as ensure robot safety and efficient energy consumption in relatively larger public-type building environments. Full article
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Open AccessArticle
Research on Collaborative Planning and Symmetric Scheduling for Parallel Shipbuilding Projects in the Open Distributed Manufacturing Environment
Symmetry 2020, 12(1), 161; https://doi.org/10.3390/sym12010161 - 13 Jan 2020
Cited by 1 | Viewed by 742
Abstract
In the current distributed manufacturing environment, more extensive enterprise cooperation is an effective means for shipbuilding companies to increase the competitiveness. However, considering the project scale and the uneven production capacity between the collaborative enterprises, a key issue for shipbuilding companies is to [...] Read more.
In the current distributed manufacturing environment, more extensive enterprise cooperation is an effective means for shipbuilding companies to increase the competitiveness. However, considering the project scale and the uneven production capacity between the collaborative enterprises, a key issue for shipbuilding companies is to effectively combine the product-oriented project tasks and the specialized production-oriented plants. Due to information privatization, the decision-making process of project planning and scheduling is distributed and symmetric. Existing project scheduling methods and collaboration mechanisms in the shipbuilding industry are somehow inefficient. The aim of the research is to provide an assistant decision-making method to support effective task dispatching and multi-party cooperation for better utilization of the distributed resources and to help project managers control the shipbuilding process. The article initially establishes an agent-based complex shipbuilding project collaborative planning and symmetric scheduling framework, simulating the distributed collaborative decision-making process and bridging the multi-project planning with the individual project scheduling in much detail, which fills the research gap. A negotiation method based on iterative combination auction (ICA) is further proposed to solve the integration problem of project planning and task scheduling, and an illustrative example is conducted to demonstrate the effectiveness and rationality of the methods. Finally, an application case using a prototype system on shipbuilding projects collaborative planning and scheduling will be reported as a result. Full article
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Open AccessArticle
Constitutive Model of Stress-Dependent Seepage in Columnar Jointed Rock Mass
Symmetry 2020, 12(1), 160; https://doi.org/10.3390/sym12010160 - 13 Jan 2020
Cited by 2 | Viewed by 584
Abstract
Columnar jointed rock mass (CJRM) is a highly symmetrical natural fractured structure. As the rock mass of the dam foundation of the Baihetan Hydropower Station, the study of its permeability anisotropy is of great significance to engineering safety. Based on the theory of [...] Read more.
Columnar jointed rock mass (CJRM) is a highly symmetrical natural fractured structure. As the rock mass of the dam foundation of the Baihetan Hydropower Station, the study of its permeability anisotropy is of great significance to engineering safety. Based on the theory of composite mechanics and Goodman’s joint superposition principle, the constitutive model of joints of CJRM is derived according to the Quadrangular prism, the Pentagonal prism and the Hexagonal prism model; combined with Singh’s research results on intermittent joint stress concentration, considering column deflection angles, the joint constitutive model of CJRM in three-dimensional space is established. For the CJRM in the Baihetan dam site area, the Quadrangular prism, the Pentagonal prism and the Hexagonal prism constitutive models were used to calculate the permeability coefficients of CJRM under different deflection angles. The permeability anisotropy characteristics of the three models were compared and verified by numerical simulation results. The results show that the calculation results of the Pentagonal prism model are in good agreement with the numerical simulation results. The variation of permeability coefficient under different confining pressures is compared, and the relationship between permeability coefficient and confining pressure is obtained, which accords with the negative exponential function and conforms to the general rule of joint seepage. Full article
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Open AccessArticle
Numerical Analysis of Fluid Forces for Flow Past a Square Rod with Detached Dual Control Rods at Various Gap Spacing
Symmetry 2020, 12(1), 159; https://doi.org/10.3390/sym12010159 - 13 Jan 2020
Cited by 1 | Viewed by 722
Abstract
A two-dimensional numerical study was conducted for flow past a square rod in the presence of two control rods. One is placed vertically in the upstream direction and the second one is placed horizontally in the downstream direction of the square rod. The [...] Read more.
A two-dimensional numerical study was conducted for flow past a square rod in the presence of two control rods. One is placed vertically in the upstream direction and the second one is placed horizontally in the downstream direction of the square rod. The influence of gap spacing was studied by taking g1 = 1–5 and g2 = 0.5–5 (where g1 is the gap between the upstream control rod and the main rod, and g2 is the space between the main rod and the downstream control rod) at Re = 160. The simulation results were obtained in the form of vorticity contour, drag and lift coefficients, Strouhal number, and force statistics. Under the effect of gap spacing, three different flow modes were found and named according to their behavior. It was found that the mean drag coefficient showed decreasing behavior by increasing the value of g2 continually at a fixed value of g1. The largest value of C d m e a n was found at (g1, g2) = (1, 1) and the greatest percentage reduction in C d m e a n was obtained at (g1, g2) = (1, 3), which is 139.72%. The effect of thrust was also noticed for all selected values of g1 and g2. Furthermore, it was noticed that the Strouhal number and the root mean square values of the drag and lift coefficients smaller values than the single rod values, except for the Clrms value of (g1, g2) = (1, 3) and (1, 4). Full article
(This article belongs to the Special Issue Fluid Mechanics Physical Problems and Symmetry)
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Open AccessArticle
Role of Geometric Shape in Chiral Optics
Symmetry 2020, 12(1), 158; https://doi.org/10.3390/sym12010158 - 13 Jan 2020
Cited by 1 | Viewed by 788
Abstract
The distinction of chiral and mirror symmetric objects is straightforward from a geometrical point of view. Since the biological as well as the optical activity of molecules strongly depend on their handedness, chirality has recently attracted high interest in the field of nano-optics. [...] Read more.
The distinction of chiral and mirror symmetric objects is straightforward from a geometrical point of view. Since the biological as well as the optical activity of molecules strongly depend on their handedness, chirality has recently attracted high interest in the field of nano-optics. Various aspects of associated phenomena including the influences of internal and external degrees of freedom on the optical response have been discussed. Here, we propose a constructive method to evaluate the possibility of observing any chiral response from an optical scatterer. Based on solely the T-matrix of one enantiomer, planes of minimal chiral response are located and compared to geometric mirror planes. This provides insights into the relation of geometric and optical properties and enables identifying the potential of chiral scatterers for nano-optical experiments. Full article
(This article belongs to the Special Issue Duality Symmetry)
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Open AccessArticle
The Impact of Manufacturing Flexibility and Multi-Criteria Optimization on the Sustainability of Manufacturing Systems
Symmetry 2020, 12(1), 157; https://doi.org/10.3390/sym12010157 - 12 Jan 2020
Cited by 5 | Viewed by 849
Abstract
The presented manuscript deals with the impact of manufacturing flexibility on cost-time investment as a function of sustainable production, which addresses the company’s sustainable social and environmental impact adequately. The impact of manufacturing flexibility on cost-time investment in the research sphere is not [...] Read more.
The presented manuscript deals with the impact of manufacturing flexibility on cost-time investment as a function of sustainable production, which addresses the company’s sustainable social and environmental impact adequately. The impact of manufacturing flexibility on cost-time investment in the research sphere is not described, despite the fact that we know its key role in the high-mix low-volume production types. Recently, researchers have been addressing intensively the impacts of various parameters on the sustainable aspect and its dependence on manufacturing flexibility. The complexity of the influence parameters is reflected in the multi-criteria nature of optimization problems that can be solved with appropriate use of the evolutionary computation methods. The manuscript presents a new method of manufacturing flexibility modelling, with respect to the four-level architectural model, which reflected as a symmetry phenomena influence on the cost-time profile diagram. The solution to a complex optimization problem is derived using the proposed improved heuristic Kalman algorithm method. A new method is presented of optimization parameters’ evaluation with respect to the manufacturing flexibility impacts on cost-time investment. The large impact of appropriate multi-criteria optimization on a sustainably justified production system is presented, with the experimental work on benchmark datasets and an application case. The new method allows a comprehensive optimization approach, and validation of the optimization results by which we can provide more sustainable products, manufacturing processes, and increase the company’s total, social and environmental benefits. Full article
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Open AccessArticle
Family Symmetries and Multi Higgs Doublet Models
Symmetry 2020, 12(1), 156; https://doi.org/10.3390/sym12010156 - 12 Jan 2020
Viewed by 801
Abstract
Imposing a family symmetry on the Standard Model in order to reduce the number of its free parameters, due to the Schur’s Lemma, requires an explicit breaking of this symmetry. To avoid the need for this symmetry to break, additional Higgs doublets can [...] Read more.
Imposing a family symmetry on the Standard Model in order to reduce the number of its free parameters, due to the Schur’s Lemma, requires an explicit breaking of this symmetry. To avoid the need for this symmetry to break, additional Higgs doublets can be introduced. In such an extension of the Standard Model, we investigate family symmetries of the Yukawa Lagrangian. We find that adding a second Higgs doublet (2HDM) does not help, at least for finite subgroups of the U ( 3 ) group up to the order of 1025. Full article
Open AccessArticle
A Method of Generating Fuzzy Implications with Specific Properties
Symmetry 2020, 12(1), 155; https://doi.org/10.3390/sym12010155 - 12 Jan 2020
Cited by 1 | Viewed by 678
Abstract
In this paper we introduce a new method of generating fuzzy implications via known fuzzy implications. We focus on the case of generating fuzzy implications via a fuzzy connective and at least one known fuzzy implication. We present some basic desirable properties of [...] Read more.
In this paper we introduce a new method of generating fuzzy implications via known fuzzy implications. We focus on the case of generating fuzzy implications via a fuzzy connective and at least one known fuzzy implication. We present some basic desirable properties of fuzzy implications that are invariant via this method. Furthermore, we suggest some ways of preservation or violation of these properties, based in this method. We show how we can generate not greater or not weaker fuzzy implications with specific properties. Finally, two subclasses of any fuzzy implication arise, the so called T and S subclasses. Full article
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