Nothing Special   »   [go: up one dir, main page]
Next Issue
Volume 12, March
Previous Issue
Volume 12, January
You seem to have javascript disabled. Please note that many of the page functionalities won't work as expected without javascript enabled.
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
5.4
2.2
Journals
Symmetry
Volume 12
Issue 2
share announcement

Symmetry, Volume 12, Issue 2 (February 2020) – 140 articles

Cover Story (view full-size image): The wave-front dynamics of gravitational signals is determined by the manifestly covariant Hamilton–Jacobi theory of classical general relativity. Arbitrary wave fronts corresponding to space-–time solutions of the non-linear set of Einstein field equations always propagate at the invariant speed of light in terms of a prescribed covariant wave equation. The picture is a sunset over the sea and was taken by Grignano (Trieste, Italy) on 24 September, 2016. The composite effect of grazing light and the surface wave pattern profile inspired our research on gravitational wave-front propagation phenomena. View this paper.
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
23 pages, 14760 KiB  
Article
LiDAR and Camera Fusion Approach for Object Distance Estimation in Self-Driving Vehicles
by G Ajay Kumar, Jin Hee Lee, Jongrak Hwang, Jaehyeong Park, Sung Hoon Youn and Soon Kwon
Symmetry 2020, 12(2), 324; https://doi.org/10.3390/sym12020324 - 24 Feb 2020
Cited by 80 | Viewed by 37356
Abstract
The fusion of light detection and ranging (LiDAR) and camera data in real-time is known to be a crucial process in many applications, such as in autonomous driving, industrial automation, and robotics. Especially in the case of autonomous vehicles, the efficient fusion of [...] Read more.
The fusion of light detection and ranging (LiDAR) and camera data in real-time is known to be a crucial process in many applications, such as in autonomous driving, industrial automation, and robotics. Especially in the case of autonomous vehicles, the efficient fusion of data from these two types of sensors is important to enabling the depth of objects as well as the detection of objects at short and long distances. As both the sensors are capable of capturing the different attributes of the environment simultaneously, the integration of those attributes with an efficient fusion approach greatly benefits the reliable and consistent perception of the environment. This paper presents a method to estimate the distance (depth) between a self-driving car and other vehicles, objects, and signboards on its path using the accurate fusion approach. Based on the geometrical transformation and projection, low-level sensor fusion was performed between a camera and LiDAR using a 3D marker. Further, the fusion information is utilized to estimate the distance of objects detected by the RefineDet detector. Finally, the accuracy and performance of the sensor fusion and distance estimation approach were evaluated in terms of quantitative and qualitative analysis by considering real road and simulation environment scenarios. Thus the proposed low-level sensor fusion, based on the computational geometric transformation and projection for object distance estimation proves to be a promising solution for enabling reliable and consistent environment perception ability for autonomous vehicles. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Overview of the proposed method. Light detection and ranging (LiDAR): light detection and ranging.</p> Full article ">Figure 2
<p>Process flow of the algorithm of the proposed method.</p> Full article ">Figure 3
<p>Sensor setup on the vehicle platform (top view).</p> Full article ">Figure 4
<p>Appearance and placement of the mounted sensors.</p> Full article ">Figure 5
<p>The planar marker board used for (<b>a</b>) intrinsic and (<b>b</b>) extrinsic parameter estimation.</p> Full article ">Figure 6
<p>An example of the LiDAR area corresponding to the camera field of view (FOV).</p> Full article ">Figure 7
<p>Projected point cloud using the camera’s intrinsic parameters.</p> Full article ">Figure 8
<p>Circles detected from the point cloud.</p> Full article ">Figure 9
<p>Circles detected from the camera image.</p> Full article ">Figure 10
<p>Distance measurement using a camera image.</p> Full article ">Figure 11
<p>Point cloud alignment on the image.</p> Full article ">Figure 12
<p>Data fusion results of object detection and classification.</p> Full article ">Figure 13
<p>Data fusion for the distance estimation process.</p> Full article ">Figure 14
<p>An autonomous vehicle equipped with LiDAR and camera sensors.</p> Full article ">Figure 15
<p>Sample snapshot dataset acquired by considering multiple on-road scenarios.</p> Full article ">Figure 16
<p>The planar marker board showing three different test cases.</p> Full article ">Figure 17
<p>Output of data fusion for detecting vehicles.</p> Full article ">Figure 18
<p>The experimental scenario for quantitative evaluation.</p> Full article ">Figure 19
<p>Data fusion using LGSVL simulator data.</p> Full article ">
22 pages, 5292 KiB  
Article
Elastic-Plastic-Damaged Zones around a Deep Circular Wellbore under Non-Uniform Loading
by Xiaoji Shang and Zhizhen Zhang
Symmetry 2020, 12(2), 323; https://doi.org/10.3390/sym12020323 - 24 Feb 2020
Cited by 5 | Viewed by 3860
Abstract
Wellbores are largely constructed during coal mining, shale gas production, and geothermal exploration. Studying the shape and size of the disturbed zone in surrounding rock is of great significance for wellbore stability control. In this paper, a theoretical model for elastic-plastic-damage analysis around [...] Read more.
Wellbores are largely constructed during coal mining, shale gas production, and geothermal exploration. Studying the shape and size of the disturbed zone in surrounding rock is of great significance for wellbore stability control. In this paper, a theoretical model for elastic-plastic-damage analysis around a deep circular wellbore under non-uniform compression is proposed. Based on the elastoplastic softening constitutive model and Mohr-Coulomb strength criterion, the analytical expressions of stresses in the elastic, plastic and damaged zones around a circle wellbore are derived. Further, the boundary line equations among the three zones are obtained according to the conditions of stress continuity. Then, the influence rules of non-uniform in-situ stress and mechanical parameters on the stress distribution and plastic zone size in surrounding rock mass are analyzed. The plastic and the damaged zones are both approximately elliptical in shape. When the lateral stress coefficient of the in-situ stress field takes the value 1, the model degenerates into the Yuan Wenbo’s Solution. If the brittleness coefficient of the surrounding rock is 0, the model degenerates into the Kastner’s Equation. Finally, the results are compared with those under two special cases (in the elastoplastic softening rock under a uniform stress field, in the ideal elastoplastic rock under a non-uniform stress field) and a common approximation method (the perturbation method). Full article
(This article belongs to the Special Issue Symmetry in Engineering Sciences II)
►▼ Show Figures

Figure 1

Figure 1
<p>Rock mass behavior models (modified from Reference [<a href="#B18-symmetry-12-00323" class="html-bibr">18</a>]).</p> Full article ">Figure 2
<p>Deep buried wellbore.</p> Full article ">Figure 3
<p>The elastoplastic softening model and the three different zones around a circle wellbore.</p> Full article ">Figure 4
<p>Schematic diagram of stress field decomposition: (<b>a</b>) the in-situ stress field, (<b>b</b>) the uniform compressive stress field, (<b>c</b>) the two-sided compressive and two-sided tensile stress field.</p> Full article ">Figure 5
<p>The radial and hoop stress in the surrounding rock mass with different internal friction angles.</p> Full article ">Figure 6
<p>The radial and hoop stress in the surrounding rock mass with different cohesion.</p> Full article ">Figure 7
<p>The radial and hoop stress in the surrounding rock mass under different lateral stress coefficients.</p> Full article ">Figure 8
<p>The effect of the internal friction angle on the radius of the plastic zone.</p> Full article ">Figure 9
<p>The effect of cohesion on the radius of the plastic zone.</p> Full article ">Figure 10
<p>The effect of the brittleness coefficient on the radius of the plastic zone.</p> Full article ">Figure 11
<p>The effect of the lateral stress coefficient on the radius of the plastic zone.</p> Full article ">Figure 12
<p>Comparison of the plastic zone and the damaged zone in surrounding rock under the non-uniform stress field (NUSF) and uniform stress field (USF).</p> Full article ">Figure 13
<p>Comparison of plastic zone shape between elastoplastic softening model and ideal elastoplastic model with different internal friction angles.</p> Full article ">Figure 14
<p>Comparison of plastic zone shape between elastoplastic softening model and ideal elastoplastic model with different cohesion.</p> Full article ">Figure 15
<p>Comparison between the proposed method and the perturbation method.</p> Full article ">
14 pages, 341 KiB  
Article
Optimal Location and Sizing of PV Sources in DC Networks for Minimizing Greenhouse Emissions in Diesel Generators
by Oscar Danilo Montoya, Luis Fernando Grisales-Noreña, Walter Gil-González, Gerardo Alcalá and Quetzalcoatl Hernandez-Escobedo
Symmetry 2020, 12(2), 322; https://doi.org/10.3390/sym12020322 - 24 Feb 2020
Cited by 37 | Viewed by 3562
Abstract
This paper addresses the problem of the optimal location and sizing of photovoltaic (PV) sources in direct current (DC) electrical networks considering time-varying load and renewable generation curves. To represent this problem, a mixed-integer nonlinear programming (MINLP) model is developed. The main idea [...] Read more.
This paper addresses the problem of the optimal location and sizing of photovoltaic (PV) sources in direct current (DC) electrical networks considering time-varying load and renewable generation curves. To represent this problem, a mixed-integer nonlinear programming (MINLP) model is developed. The main idea of including PV sources in the DC grid is minimizing the total greenhouse emissions produced by diesel generators in isolated areas. An artificial neural network is employed for short-term forecasting to deal with uncertainties in the PV power generation. The general algebraic modeling system (GAMS) package is employed to solve the MINLP model by using the CONOPT solver that works with mixed and integer variables. Numerical results demonstrate important reductions of harmful gas emissions to the atmosphere when PV sources are optimally integrated (size and location) to the DC grid. Full article
(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)
►▼ Show Figures

Figure 1

Figure 1
<p>Historical data for solar prediction (adapted from [<a href="#B4-symmetry-12-00322" class="html-bibr">4</a>,<a href="#B50-symmetry-12-00322" class="html-bibr">50</a>]).</p> Full article ">Figure 2
<p>ANN scheme for solar radiation prediction [<a href="#B50-symmetry-12-00322" class="html-bibr">50</a>].</p> Full article ">Figure 3
<p>Electrical configuration for the 21-node test system.</p> Full article ">Figure 4
<p>Total reductions in <math display="inline"><semantics> <mrow> <mi>C</mi> <msub> <mi>O</mi> <mn>2</mn> </msub> </mrow> </semantics></math> emissions per day for each simulation scenario.</p> Full article ">Figure 5
<p>Generation profiles of the diesel sources during the day.</p> Full article ">
13 pages, 1557 KiB  
Article
Energy of Accelerations Used to Obtain the Motion Equations of a Three- Dimensional Finite Element
by Sorin Vlase, Iuliu Negrean, Marin Marin and Maria Luminița Scutaru
Symmetry 2020, 12(2), 321; https://doi.org/10.3390/sym12020321 - 23 Feb 2020
Cited by 32 | Viewed by 2727
Abstract
When analyzing the dynamic behavior of multi-body elastic systems, a commonly used method is the finite element method conjunctively with Lagrange’s equations. The central problem when approaching such a system is determining the equations of motion for a single finite element. The paper [...] Read more.
When analyzing the dynamic behavior of multi-body elastic systems, a commonly used method is the finite element method conjunctively with Lagrange’s equations. The central problem when approaching such a system is determining the equations of motion for a single finite element. The paper presents an alternative method of calculation theses using the Gibbs–Appell (GA) formulation, which requires a smaller number of calculations and, as a result, is easier to apply in practice. For this purpose, the energy of the accelerations for one single finite element is calculated, which will be used then in the GA equations. This method can have advantages in applying to the study of multi-body systems with elastic elements and in the case of robots and manipulators that have in their composition some elastic elements. The number of differentiation required when using the Gibbs–Appell method is smaller than if the Lagrange method is used which leads to a smaller number of operations to obtain the equations of motion. Full article
(This article belongs to the Special Issue Multibody Systems with Flexible Elements)
►▼ Show Figures

Figure 1

Figure 1
<p>Three-dimensional finite element.</p> Full article ">Figure 2
<p>(<b>a</b>) Experimental test stand and (<b>b</b>) sketch of the mechanism with the positioning of the markers (dimensions are in mm). 1—engine; 2—rotating disk; 3—invertor; 4—pumps; 5—valves; 6—rod; 7—pendulum rod; 8—weight.</p> Full article ">Figure 3
<p>Sketch of the motion of the two degree of freedom system for the angular speed 16 rad/s.</p> Full article ">Figure 4
<p>Sketch of the motion of the two degree of freedom system for the angular speed 19 rad/s.</p> Full article ">
15 pages, 2887 KiB  
Review
The Pauli Exclusion Principle and the Problems of Its Experimental Verification
by Ilya G. Kaplan
Symmetry 2020, 12(2), 320; https://doi.org/10.3390/sym12020320 - 23 Feb 2020
Cited by 18 | Viewed by 7694
Abstract
The modern state of the Pauli exclusion principle is shortly discussed. We describe the discovery by Pauli, his principle for electrons, and how it was generalized for all elementary particles in the framework of quantum mechanics. The motivations and theoretical conceptions that induced [...] Read more.
The modern state of the Pauli exclusion principle is shortly discussed. We describe the discovery by Pauli, his principle for electrons, and how it was generalized for all elementary particles in the framework of quantum mechanics. The motivations and theoretical conceptions that induced the experiments for verification of the Pauli exclusion principle are analyzed. The results and methodology of two different types of experiments are discussed: (1) the search of unusual atoms and nuclei in the stable non-Pauli states, and (2) the experiments in which the emitted radiation of non-Pauli transitions is measured. In conclusion, the comments on the discussed experiments that follow from the general quantum mechanical conceptions and group theory are formulated. Full article
(This article belongs to the Special Issue Symmetries and the Pauli Exclusion Principle)
►▼ Show Figures

Figure 1

Figure 1
<p>The statistics of composite particles.</p> Full article ">Figure 2
<p>Scheme of permitted radiative transition to K-shell, if the 1<span class="html-italic">s</span> electron undergoes spontaneous decay.</p> Full article ">Figure 3
<p>The schematic representation of the formation of the Pauli-forbidden K-shell population in experiments of the Ramberg and Snow type.</p> Full article ">
20 pages, 6523 KiB  
Article
Facial Expression Recognition by Regional Weighting with Approximated Q-Learning
by Seong-Gi Oh and TaeYong Kim
Symmetry 2020, 12(2), 319; https://doi.org/10.3390/sym12020319 - 23 Feb 2020
Cited by 4 | Viewed by 2782
Abstract
Several facial expression recognition methods cluster facial elements according to similarity and weight them considering the importance of each element in classification. However, these methods are limited by the pre-definitions of units restricting modification of the structure during optimization. This study proposes a [...] Read more.
Several facial expression recognition methods cluster facial elements according to similarity and weight them considering the importance of each element in classification. However, these methods are limited by the pre-definitions of units restricting modification of the structure during optimization. This study proposes a modified support vector machine classifier called Grid Map, which is combined with reinforcement learning to improve the classification accuracy. To optimize training, the input image size is normalized according to the cascade rules of a pre-processing detector, and the regional weights are assigned by an adaptive cell size that divides each region of the image using bounding grids. Reducing the size of the bounding grid reduces the area used for feature extraction, allowing more detailed weighted features to be extracted. Error-correcting output codes with a histogram of gradient is selected as the classification method via an experiment to determine the optimal feature and classifier selection. The proposed method is formulated into a decision process and solved via Q-learning. To classify seven emotions, the proposed method exhibits accuracies of 96.36% and 98.47% for four databases and Extended Cohn-–Kanade Dataset (CK+), respectively. Compared to the basic method exhibiting a similar accuracy, the proposed method requires 68.81% fewer features and only 66.33% of the processing time. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Error-correcting output codes (ECOC) bit structure of one vs. all (OVA) (left) and ordinal (right) for seven classes.</p> Full article ">Figure 2
<p>ECOC bit structure of one vs. one (OVO) for seven classes.</p> Full article ">Figure 3
<p>Areas that influenced by size 30 (<b>left</b>) and 15 (<b>right</b>).</p> Full article ">Figure 4
<p>Examples of feature extraction cell distribution in the basic method (<b>left</b>) and Grid Map (<b>right</b>).</p> Full article ">Figure 5
<p>Adaptive feature extraction with padding.</p> Full article ">Figure 6
<p>The flow chart of adaptive feature extraction. HOG: histogram of gradients.</p> Full article ">Figure 7
<p>The initial state of training stage of Grid Map in one-way decision process.</p> Full article ">Figure 8
<p>The second state of training stage of Grid Map in one-way decision process.</p> Full article ">Figure 9
<p>A frame in S052.004 sequence of the Extended Cohn–Kanade Dataset (CK+) database.</p> Full article ">Figure 10
<p>Five images from the modified CK+ database acquired via database regularization with the same cascade rules.</p> Full article ">Figure 11
<p>Optimal Grid Map through CK+ database.</p> Full article ">Figure 12
<p>Classification accuracy improvement value according to padding.</p> Full article ">Figure 13
<p>Classification accuracy chart of w padding and w/o padding.</p> Full article ">Figure 14
<p>Classification accuracy using the CK+ database.</p> Full article ">Figure 15
<p>Classification accuracy according to the resolutions (res_) 128 × 128, 256 × 256, 512 × 512.</p> Full article ">Figure 16
<p>Visualization of optimal Grid Map according to normalized resolution.</p> Full article ">Figure 17
<p>Feature extractor cell distribution of the basic HOG (<b>left</b>) and Grid Map (<b>right</b>).</p> Full article ">Figure 18
<p>S062_002 and S063_001 sequence, in which the camera or actor’s face was transformed.</p> Full article ">
11 pages, 1845 KiB  
Article
The Impact of Herding Tendency in Modular Networks on the Diffusion of Internet Investment Products
by Xiaokang Cheng, Narisa Zhao and Chenqi Li
Symmetry 2020, 12(2), 318; https://doi.org/10.3390/sym12020318 - 23 Feb 2020
Cited by 1 | Viewed by 2620
Abstract
In this paper, we aim to study the impact of the shift in herding tendency on the diffusion of internet investment products in modular social networks. The epidemic spreading mechanism is applied and numerical analyses are conducted. The results suggest that the increase [...] Read more.
In this paper, we aim to study the impact of the shift in herding tendency on the diffusion of internet investment products in modular social networks. The epidemic spreading mechanism is applied and numerical analyses are conducted. The results suggest that the increase in herding tendency slows down the diffusion process and postpones the outbreak time of the diffusion, but such negative effects can be compromised when the independent acceptance willingness is high. When independent acceptance willingness is low, the limited extent of the herding tendency increases the diffusion scope. In addition, the expansion of the propagation lifetime or the increase of the clustering coefficient increases the threshold so that the herding tendency has an effect on outbreak size. Further, the growth of the herding propensity tends to magnify the positive influence of the clustering coefficient and the negative effect of the modularity. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>(<b>a</b>) The contagion mechanism of investment decisions. (<b>b</b>) The diffusion process of an Internet investment product (IIP).</p> Full article ">Figure 2
<p>(<b>a</b>) The numbers of potential investor (P), investor (I), divestor (D), and regular investor (RI) nodes against time t. (<b>b</b>) Comparison between the real data and the theoretical result of R(t).</p> Full article ">Figure 3
<p>The number of regular investors against time t with varying herding tendency τ. (<b>a</b>) Independent acceptance willingness ω = 0.1, (<b>b</b>) ω = 0.5, (<b>c</b>) ω = 0.9. (<b>d</b>) The final propagation scope versus τ with timespan T = 50,000, 100,000, 150,000, and 200,000, respectively. Other parameters are the same as the default settings.</p> Full article ">Figure 4
<p>Number of regular investors against time t with different mean values of clustering coefficients (i.e., b = 0.1, 0.5, and 0.9, respectively). (<b>a</b>) Herding tendency τ = 0.6, (<b>b</b>) τ = 0.7, (<b>c</b>) τ = 0.8. Other parameters are the same as the default setting.</p> Full article ">Figure 5
<p>Number of regular investors against time t with modularity Q = 0.1, 0.5, and 0.9, respectively. (<b>a</b>) Herding tendency τ = 0.6, (<b>b</b>) τ = 0.7, (<b>c</b>) τ = 0.8. Other parameters are the same as the default setting.</p> Full article ">Figure 6
<p>(<b>a</b>) Number of R nodes with a changing clustering coefficient and herding tendency τ. (<b>b</b>) Number of R nodes with changing modularity Q and herding propensity τ. Other parameters are the same as the default setting.</p> Full article ">
29 pages, 930 KiB  
Article
Elastic Deformations and Wigner–Weyl Formalism in Graphene
by I.V. Fialkovsky and M.A. Zubkov
Symmetry 2020, 12(2), 317; https://doi.org/10.3390/sym12020317 - 23 Feb 2020
Cited by 16 | Viewed by 3111
Abstract
We discuss the tight-binding models of solid state physics with the Z 2 sublattice symmetry in the presence of elastic deformations in an important particular case—the tight binding model of graphene. In order to describe the dynamics of electronic quasiparticles, the Wigner–Weyl formalism [...] Read more.
We discuss the tight-binding models of solid state physics with the Z 2 sublattice symmetry in the presence of elastic deformations in an important particular case—the tight binding model of graphene. In order to describe the dynamics of electronic quasiparticles, the Wigner–Weyl formalism is explored. It allows the calculation of the two-point Green’s function in the presence of two slowly varying external electromagnetic fields and the inhomogeneous modification of the hopping parameters that result from elastic deformations. The developed formalism allows us to consider the influence of elastic deformations and the variations of magnetic field on the quantum Hall effect. Full article
(This article belongs to the Special Issue Relations between Condensed Matter Physics and Relativistic Quantum Field Theory)
19 pages, 2737 KiB  
Article
A Shift-Dependent Measure of Extended Cumulative Entropy and Its Applications in Blind Image Quality Assessment
by Saeid Tahmasebi, Ahmad Keshavarz, Maria Longobardi and Reza Mohammadi
Symmetry 2020, 12(2), 316; https://doi.org/10.3390/sym12020316 - 23 Feb 2020
Cited by 5 | Viewed by 2671
Abstract
Recently, Tahmasebi and Eskandarzadeh introduced a new extended cumulative entropy (ECE). In this paper, we present results on shift-dependent measure of ECE and its dynamic past version. These results contain stochastic order, upper and lower bounds, the symmetry property and some relationships with [...] Read more.
Recently, Tahmasebi and Eskandarzadeh introduced a new extended cumulative entropy (ECE). In this paper, we present results on shift-dependent measure of ECE and its dynamic past version. These results contain stochastic order, upper and lower bounds, the symmetry property and some relationships with other reliability functions. We also discuss some properties of conditional weighted ECE under some assumptions. Finally, we propose a nonparametric estimator of this new measure and study its practical results in blind image quality assessment. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Referenecs of horse, harbor and baby images (<b>a</b>, <b>b</b> and <b>c</b>, respectively).</p> Full article ">Figure 2
<p>Best quality images that were selected using the R<math display="inline"><semantics> <mover accent="true"> <mi>e</mi> <mo>´</mo> </mover> </semantics></math>nyi-AIQ metric from GQ, MQ and LQ distorted horse images (<b>a</b>, <b>c</b> and <b>e</b>, respectively), and best quality images that were selected using the WECE-AIQ metric from GQ, MQ and LQ distorted horse images (<b>b</b>, <b>d</b> and <b>f</b>, respectively).</p> Full article ">Figure 3
<p>Best quality images that were selected using the R<math display="inline"><semantics> <mover accent="true"> <mi>e</mi> <mo>´</mo> </mover> </semantics></math>nyi-AIQ metric from GQ, MQ and LQ distorted harbor images (<b>a</b>, <b>c</b> and <b>e</b>, respectively), and best quality images that were selected using the WECE-AIQ metric from GQ, MQ and LQ distorted harbor images (<b>b</b>, <b>d</b> and <b>f</b>, respectively).</p> Full article ">Figure 4
<p>Best quality images that were selected using the R<math display="inline"><semantics> <mover accent="true"> <mi>e</mi> <mo>´</mo> </mover> </semantics></math>nyi-AIQ metric from GQ, MQ and LQ distorted baby images (<b>a</b>, <b>c</b> and <b>e</b>, respectively), and best quality images that were selected using the WECE-AIQ metric from GQ, MQ and LQ distorted baby images (<b>b</b>, <b>d</b> and <b>f</b>, respectively).</p> Full article ">
21 pages, 486 KiB  
Article
Some Results on Various Cancellative CA-Groupoids and Variant CA-Groupoids
by Zhirou Ma, Xiaohong Zhang and Florentin Smarandache
Symmetry 2020, 12(2), 315; https://doi.org/10.3390/sym12020315 - 22 Feb 2020
Cited by 2 | Viewed by 3312
Abstract
Cyclic associativity can be regarded as a kind of variation symmetry, and cyclic associative groupoid (CA-groupoid) is a generalization of commutative semigroup. In this paper, the various cancellation properties of CA-groupoids, including cancellation, quasi-cancellation and power cancellation, are studied. The relationships among cancellative [...] Read more.
Cyclic associativity can be regarded as a kind of variation symmetry, and cyclic associative groupoid (CA-groupoid) is a generalization of commutative semigroup. In this paper, the various cancellation properties of CA-groupoids, including cancellation, quasi-cancellation and power cancellation, are studied. The relationships among cancellative CA-groupoids, quasi-cancellative CA-groupoids and power cancellative CA-groupoids are found out. Moreover, the concept of variant CA-groupoid is proposed firstly, some examples are presented. It is shown that the structure of variant CA-groupoid is very interesting, and the construction methods and decomposition theorem of variant CA-groupoids are established. Full article
(This article belongs to the Special Issue Discrete Mathematics and Symmetry)
►▼ Show Figures

Figure 1

Figure 1
<p>The relationships among some CA-groupoids<b>.</b></p> Full article ">
15 pages, 1767 KiB  
Article
Analysis Exploring the Uniformity of Flow Distribution in Multi-Channels for the Application of Printed Circuit Heat Exchangers
by Hanbing Ke, Yuansheng Lin, Zhiwu Ke, Qi Xiao, Zhiguo Wei, Kai Chen and Huijin Xu
Symmetry 2020, 12(2), 314; https://doi.org/10.3390/sym12020314 - 22 Feb 2020
Cited by 16 | Viewed by 3590
Abstract
The maldistribution of fluid flow through multi-channels is a critical issue encountered in many areas, such as multi-channel heat exchangers, electronic device cooling, refrigeration and cryogenic devices, air separation and the petrochemical industry. In this paper, the uniformity of flow distribution in a [...] Read more.
The maldistribution of fluid flow through multi-channels is a critical issue encountered in many areas, such as multi-channel heat exchangers, electronic device cooling, refrigeration and cryogenic devices, air separation and the petrochemical industry. In this paper, the uniformity of flow distribution in a printed circuit heat exchanger (PCHE) is investigated. The flow distribution and resistance characteristics of a PCHE plate are studied with numerical models under different flow distribution cases. The results show that the sudden change in the angle of the fluid at the inlet of the channel can be greatly reduced by using a spreader plate with an equal inner and outer radius. The flow separation of the fluid at the inlet of the channel can also be weakened and the imbalance of flow distribution in the channel can be reduced. Therefore, the flow uniformity can be improved and the pressure loss between the inlet and outlet of PCHEs can be reduced. The flow maldistribution in each PCHE channel can be reduced to ± 0.2%, and the average flow maldistribution in all PCHE channels can be reduced to less than 5% when the number of manifolds reaches nine. The numerical simulation of fluid flow distribution can provide guidance for the subsequent research and the design and development of multi-channel heat exchangers. In summary, the symmetry of the fluid flow in multi-channels for PCHE was analyzed in this work. This work presents the frequently encountered problem of maldistribution of fluid flow in engineering, and the performance promotion leads to symmetrical aspects in both the structure and the physical process. Full article
(This article belongs to the Special Issue Recent Advances in Mathematical Aspect in Engineering)
►▼ Show Figures

Figure 1

Figure 1
<p>Heat exchanger plate with single inlet and outlet.</p> Full article ">Figure 2
<p>Heat exchanger plate with collecting flow at the inlet and outlet.</p> Full article ">Figure 3
<p>Calculation model for the multi-channel heat exchanger.</p> Full article ">Figure 4
<p>Validation of grid independence.</p> Full article ">Figure 5
<p>Configurations of different cases.</p> Full article ">Figure 6
<p>Streamlines of different cases.</p> Full article ">Figure 7
<p>Imbalance of flow distribution for different cases.</p> Full article ">Figure 8
<p>Nonuniformity of flow distribution for different cases.</p> Full article ">Figure 9
<p>Variation in the pressure drop with different velocities.</p> Full article ">Figure 10
<p>Different numbers of spreader plates.</p> Full article ">Figure 11
<p>Imbalance of flow distribution for different numbers of spreader plates.</p> Full article ">Figure 12
<p>Nonuniformity of flow distribution for different numbers of spreader plates.</p> Full article ">Figure 13
<p>Variation in the pressure drop with different numbers of spreader plates.</p> Full article ">
17 pages, 304 KiB  
Article
Symmetry of the Relativistic Two-Body Bound State
by L.P. Horwitz and R.I. Arshansky
Symmetry 2020, 12(2), 313; https://doi.org/10.3390/sym12020313 - 22 Feb 2020
Viewed by 2207
Abstract
We show that in a relativistically covariant formulation of the two-body problem, the bound state spectrum is in agreement, up to relativistic corrections, with the non-relativistic bound-state spectrum. This solution is achieved by solving the problem with support of the wave functions in [...] Read more.
We show that in a relativistically covariant formulation of the two-body problem, the bound state spectrum is in agreement, up to relativistic corrections, with the non-relativistic bound-state spectrum. This solution is achieved by solving the problem with support of the wave functions in an O ( 2 , 1 ) invariant submanifold of the Minkowski spacetime. The O ( 3 , 1 ) invariance of the differential equation requires, however, that the solutions provide a representation of O ( 3 , 1 ) . Such solutions are obtained by means of the method of induced representations, providing a basic insight into the subject of the symmetries of relativistic dynamics. Full article
(This article belongs to the Special Issue Relativity Based on Symmetry)
12 pages, 267 KiB  
Article
Schwarzschild Field of a Proper Time Oscillator
by Hou Yau
Symmetry 2020, 12(2), 312; https://doi.org/10.3390/sym12020312 - 21 Feb 2020
Viewed by 2220
Abstract
In this paper, we show that an oscillator in proper time can mimic a point mass at rest in general relativity. The spacetime outside this proper time oscillator is static and satisfies the Schwarzschild solution. Full article
13 pages, 780 KiB  
Article
An Efficient Algorithm for Eigenvalue Problem of Latin Squares in a Bipartite Min-Max-Plus System
by Mubasher Umer, Umar Hayat, Fazal Abbas, Anurag Agarwal and Petko Kitanov
Symmetry 2020, 12(2), 311; https://doi.org/10.3390/sym12020311 - 21 Feb 2020
Cited by 3 | Viewed by 2415
Abstract
In this paper, we consider the eigenproblems for Latin squares in a bipartite min-max-plus system. The focus is upon developing a new algorithm to compute the eigenvalue and eigenvectors (trivial and non-trivial) for Latin squares in a bipartite min-max-plus system. We illustrate the [...] Read more.
In this paper, we consider the eigenproblems for Latin squares in a bipartite min-max-plus system. The focus is upon developing a new algorithm to compute the eigenvalue and eigenvectors (trivial and non-trivial) for Latin squares in a bipartite min-max-plus system. We illustrate the algorithm using some examples. The proposed algorithm is implemented in MATLAB, using max-plus algebra toolbox. Computationally speaking, our algorithm has a clear advantage over the power algorithm presented by Subiono and van der Woude. Because our algorithm takes 0 . 088783 sec to solve the eigenvalue problem for Latin square presented in Example 2, while the compared one takes 1 . 718662 sec for the same problem. Furthermore, a time complexity comparison is presented, which reveals that the proposed algorithm is less time consuming when compared with some of the existing algorithms. Full article
(This article belongs to the Special Issue Symmetry in Numerical Linear and Multilinear Algebra)
21 pages, 1525 KiB  
Article
Integrated Decision-Making Approach Based on SWARA and GRA Methods for the Prioritization of Failures in Solar Panel Systems under Z-Information
by Saeid Jafarzadeh Ghoushchi, Mohd Nizam Ab Rahman, Diba Raeisi, Elnaz Osgooei and Majid Jafarzadeh Ghoushji
Symmetry 2020, 12(2), 310; https://doi.org/10.3390/sym12020310 - 21 Feb 2020
Cited by 31 | Viewed by 4115
Abstract
Encountering a problem or error in the final stages of providing products or services increases costs and delays scheduling. The key task is to ensure quality and reliability in the early stages of the production process and prevent errors from occurring from the [...] Read more.
Encountering a problem or error in the final stages of providing products or services increases costs and delays scheduling. The key task is to ensure quality and reliability in the early stages of the production process and prevent errors from occurring from the beginning. Failure mode and effect analysis (FMEA) is one of the tools for identifying potential problems and their impact on products and services. The conventional FMEA technique has been criticized extensively due to its disadvantages. In this study, the concepts of uncertainty and reliability are considered simultaneously. The processes of weighting risk factors, prioritizing failures by using the stepwise weight assessment ratio analysis (SWARA)–gray relational analysis (GRA) integrated method based on Ζ-number theory and complete prioritization of failures are implemented. Crucial management indices, such as cost and time, are considered in addition to severity, occurrence and detection factors along with assigning symmetric form of the weights to them. This, in turn, increases the interpretability of results and reduces the decision-maker’s subjectivity in risk prioritization. The developed model is implemented on solar panel data with 19 failure modes determined by the FMEA team. Results show that the proposed approach provides a more complete and realistic prioritization of failures than conventional FMEA and fuzzy GRA methods do. Full article
(This article belongs to the Special Issue Uncertain Multi-Criteria Optimization Problems)
►▼ Show Figures

Figure 1

Figure 1
<p>Symmetric triangular Fuzzy Number.</p> Full article ">Figure 2
<p>Proposed approach for prioritizing the failures of the solar panels.</p> Full article ">Figure 3
<p>Comparison of failure prioritization based on conventional FMEA, fuzzy GRA, Z-GRA approaches.</p> Full article ">Figure 4
<p>Sensitivity analysis for Z-GRA.</p> Full article ">
17 pages, 4866 KiB  
Article
Utilization of Second Order Slip, Activation Energy and Viscous Dissipation Consequences in Thermally Developed Flow of Third Grade Nanofluid with Gyrotactic Microorganisms
by Zahra Abdelmalek, Sami Ullah Khan, Hassan Waqas, Hossam A. Nabwey and Iskander Tlili
Symmetry 2020, 12(2), 309; https://doi.org/10.3390/sym12020309 - 21 Feb 2020
Cited by 47 | Viewed by 3323
Abstract
In recent decades, an interest has been developed towards the thermal consequences of nanofluid because of utilization of nano-materials to improve the thermal conductivity of traditional liquid and subsequently enhance the heat transportation phenomenon. Following this primarily concept, this current work investigates the [...] Read more.
In recent decades, an interest has been developed towards the thermal consequences of nanofluid because of utilization of nano-materials to improve the thermal conductivity of traditional liquid and subsequently enhance the heat transportation phenomenon. Following this primarily concept, this current work investigates the thermal developed flow of third-grade nanofluid configured by a stretched surface with additional features of activation energy, viscous dissipation and second-order slip. Buongiorno’s nanofluid model is used to explore the thermophoresis and Brownian motion features based on symmetry fundamentals. It is further assumed that the nanoparticles contain gyrotactic microorganisms, which are associated with the most fascination bioconvection phenomenon. The flow problem owing to the partial differential equations is renovated into dimensional form, which is numerically simulated with the help of bvp4c, by using MATLAB software. The aspects of various physical parameters associated to the current analysis are graphically examined against nanoparticles’ velocity, temperature, concentration and gyrotactic microorganisms’ density distributions. Further, the objective of local Nusselt number, local Sherwood number and motile density number are achieved numerically with variation of various parameters. The results presented here may find valuable engineering applications, like cooling liquid metals, solar systems, power production, solar energy, thermal extrusion systems cooling of machine equipment, transformer oil and microelectronics. Further, flow of nanoparticles containing gyrotactic microorganisms has interesting applications in microbial fuel cells, microfluidic devices, bio-technology and enzyme biosensors. Full article
(This article belongs to the Special Issue Future and Prospects in Non-Newtonian and Nanofluids)
►▼ Show Figures

Figure 1

Figure 1
<p>Change in <math display="inline"><semantics> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> </mrow> </semantics></math> with <math display="inline"><semantics> <mrow> <mi>N</mi> <mi>r</mi> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>N</mi> <mi>c</mi> <mo>.</mo> </mrow> </semantics></math>.</p> Full article ">Figure 2
<p>Change in <math display="inline"><semantics> <mrow> <msup> <mi>f</mi> <mo>′</mo> </msup> </mrow> </semantics></math> with <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>β</mi> <mo>.</mo> </mrow> </semantics></math></p> Full article ">Figure 3
<p>Change in <math display="inline"><semantics> <mi>θ</mi> </semantics></math> with <math display="inline"><semantics> <mrow> <mi>P</mi> <mi>r</mi> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>R</mi> <mi>d</mi> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>Change in <math display="inline"><semantics> <mi>θ</mi> </semantics></math> with <math display="inline"><semantics> <mi>K</mi> </semantics></math> and <math display="inline"><semantics> <mo>Ω</mo> </semantics></math>.</p> Full article ">Figure 5
<p>Change in <math display="inline"><semantics> <mi>θ</mi> </semantics></math> with <math display="inline"><semantics> <mrow> <mi>B</mi> <mi>i</mi> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>N</mi> <mi>t</mi> </mrow> </semantics></math>.</p> Full article ">Figure 6
<p>Change in <math display="inline"><semantics> <mi>θ</mi> </semantics></math> with <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math>.</p> Full article ">Figure 7
<p>Change in <math display="inline"><semantics> <mi>θ</mi> </semantics></math> with <math display="inline"><semantics> <mo>Λ</mo> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>Re</mi> </mrow> </semantics></math>.</p> Full article ">Figure 8
<p>Change in <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math> for <math display="inline"><semantics> <mrow> <mi>N</mi> <mi>b</mi> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>L</mi> <mi>e</mi> </mrow> </semantics></math>.</p> Full article ">Figure 9
<p>Change in <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math> for <math display="inline"><semantics> <mi>E</mi> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>P</mi> <mi>r</mi> <mo>.</mo> </mrow> </semantics></math>.</p> Full article ">Figure 10
<p>Change in <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math> for <math display="inline"><semantics> <mo>Λ</mo> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>Re</mi> </mrow> </semantics></math>.</p> Full article ">Figure 11
<p>Change in <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math> for <math display="inline"><semantics> <mi>K</mi> </semantics></math> and <math display="inline"><semantics> <mo>Ω</mo> </semantics></math>.</p> Full article ">Figure 12
<p>Change in <math display="inline"><semantics> <mi>ϕ</mi> </semantics></math> for <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math>.</p> Full article ">Figure 13
<p>Change in <math display="inline"><semantics> <mi>χ</mi> </semantics></math> for <math display="inline"><semantics> <mi>α</mi> </semantics></math> and <math display="inline"><semantics> <mi>β</mi> </semantics></math>.</p> Full article ">Figure 14
<p>Change in <math display="inline"><semantics> <mi>χ</mi> </semantics></math> for <math display="inline"><semantics> <mo>Λ</mo> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>Re</mi> </mrow> </semantics></math>.</p> Full article ">Figure 15
<p>Change in <math display="inline"><semantics> <mi>χ</mi> </semantics></math> for <math display="inline"><semantics> <mi>K</mi> </semantics></math> and <math display="inline"><semantics> <mo>Ω</mo> </semantics></math>.</p> Full article ">Figure 16
<p>Change in <math display="inline"><semantics> <mi>χ</mi> </semantics></math> for <math display="inline"><semantics> <mrow> <mi>P</mi> <mi>e</mi> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <mi>L</mi> <mi>b</mi> </mrow> </semantics></math>.</p> Full article ">
26 pages, 851 KiB  
Article
Quantum Analogs of Ostrowski-Type Inequalities for Raina’s Function correlated with Coordinated Generalized Φ-Convex Functions
by Hong-Hu Chu, Humaira Kalsoom, Saima Rashid, Muhammad Idrees, Farhat Safdar, Yu-Ming Chu and Dumitru Baleanu
Symmetry 2020, 12(2), 308; https://doi.org/10.3390/sym12020308 - 21 Feb 2020
Cited by 17 | Viewed by 2218
Abstract
In this paper, the newly proposed concept of Raina’s function and quantum calculus are utilized to anticipate the quantum behavior of two variable Ostrowski-type inequalities. This new technique is the convolution of special functions with hypergeometric and Mittag–Leffler functions, respectively. This new concept [...] Read more.
In this paper, the newly proposed concept of Raina’s function and quantum calculus are utilized to anticipate the quantum behavior of two variable Ostrowski-type inequalities. This new technique is the convolution of special functions with hypergeometric and Mittag–Leffler functions, respectively. This new concept will have the option to reduce self-similitudes in the quantum attractors under investigation. We discuss the implications and other consequences of the quantum Ostrowski-type inequalities by deriving an auxiliary result for a q 1 q 2 -differentiable function by inserting Raina’s functions. Meanwhile, we present a numerical scheme that can be used to derive variants for Ostrowski-type inequalities in the sense of coordinated generalized Φ -convex functions with the quantum approach. This new scheme of study for varying values of parameters with the involvement of Raina’s function yields extremely intriguing outcomes with an illustrative example. It is supposed that this investigation will provide new directions for the capricious nature of quantum theory. Full article
20 pages, 10694 KiB  
Article
Implementing CCTV-Based Attendance Taking Support System Using Deep Face Recognition: A Case Study at FPT Polytechnic College
by Ngo Tung Son, Bui Ngoc Anh, Tran Quy Ban, Le Phuong Chi, Bui Dinh Chien, Duong Xuan Hoa, Le Van Thanh, Tran Quang Huy, Le Dinh Duy and Muhammad Hassan Raza Khan
Symmetry 2020, 12(2), 307; https://doi.org/10.3390/sym12020307 - 21 Feb 2020
Cited by 15 | Viewed by 18867
Abstract
Face recognition (FR) has received considerable attention in the field of security, especially in the use of closed-circuit television (CCTV) cameras in security monitoring. Although significant advances in the field of computer vision are made, advanced face recognition systems provide satisfactory performance only [...] Read more.
Face recognition (FR) has received considerable attention in the field of security, especially in the use of closed-circuit television (CCTV) cameras in security monitoring. Although significant advances in the field of computer vision are made, advanced face recognition systems provide satisfactory performance only in controlled conditions. They deteriorate significantly in the face of real-world scenarios such as lighting conditions, motion blur, camera resolution, etc. This article shows how we design, implement, and conduct the empirical comparisons of machine learning open libraries in building attendance taking (AT) support systems using indoor security cameras called ATSS. Our trial system was deployed to record the appearances of 120 students in five classes who study on the third floor of FPT Polytechnic College building. Our design allows for flexible system scaling, and it is not only usable for a school but a generic attendance system with CCTV. The measurement results show that the accuracy is suitable for many different environments. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Real installation of the attendance taking support system (ATSS) at the third floor at FPT Polytechnic School.</p> Full article ">Figure 2
<p>Illustration of three main components of the deep face system. (<b>A</b>) demonstrates the face detection from an image frame, (<b>B</b>) shows the landmarks points of the cropped faces, and (<b>C</b>) plot featured data in feature space archived by feature descriptor.</p> Full article ">Figure 3
<p>ATSS system architecture.</p> Full article ">Figure 4
<p>Class diagram represents the data structure of exchanged data between the ATSS and the academic portal. Classes and relationships are described in black to represent the data that ATSS receives from the academic portal. The classes and relationships highlighted.</p> Full article ">Figure 5
<p>Archived image frames from CCTV are divided into jobs and stores in the queue for next process.</p> Full article ">Figure 6
<p>Components of an Ai processing unit.</p> Full article ">Figure 7
<p>Example of nine faces collected of a particular student.</p> Full article ">Figure 8
<p>Illustration of the similarity between the test faces and the mean of the training faces (Euclidean distance, the closer is better) corresponding to a particular range to camera.</p> Full article ">Figure 9
<p>Example of connected bounding boxes.</p> Full article ">Figure 10
<p>Example of a sliding window.</p> Full article ">Figure 11
<p>Example of the output of the summarization algorithm. (<b>A</b>) Illustrates the pure classification results. (<b>B</b>) The most frequent label (class) assigned to the whole boxes appear in the window.</p> Full article ">Figure 12
<p>The frequencies of appearance of 60 labels (including unknown) in the test set. The first chart represents the number of unknown samples in the test set.</p> Full article ">Figure 13
<p>(<b>A</b>) The heat map to represent training set in feature space, learned by Arcface. (<b>B</b>) The extracted vectors by FaceNet visualized in two dimensions space by t-SNE.</p> Full article ">Figure 14
<p>(<b>A</b>) The heat map to represent training set in feature space, learned by Arcface. (<b>B</b>) The extracted vectors by Arcface visualized in two dimensions space by t-SNE.</p> Full article ">Figure 15
<p>Inter-class and intra-class distance of face representation computed by Facenet and Arcface.</p> Full article ">Figure 16
<p>Confusion matrix archived from the combination of Arcface (pre-trained model <span class="html-italic">LResNet100E</span>-IR, ArcFace@ms1m-refine-v2) and KNN (K = 5 and confident distance threshold = 1.07). The first column and row represent the label of “unknown,” other columns and rows show the result of corresponding class. Displayed data is normalized because of the large number of “unknown” samples.</p> Full article ">Figure 17
<p>The obtained confusion matrix after executing summarization process. The first column and row represent the label of “unknown,” other columns and rows show the result of corresponding class. Displayed data are normalized because of the large number of “unknown” samples.</p> Full article ">Figure 18
<p>(<b>A</b>) shows the processing time of the FR processing. (<b>B</b>) illustrate the processing time of face detection (including landmarks points) and face alignment. (<b>C</b>) visualizes the processing time of face description, corresponding to number of faces in the same.</p> Full article ">Figure 19
<p>(<b>A</b>) total processing time on 12 videos using different number of workers. (<b>B</b>) CPU usage in percentage on 12 videos using different number of workers. (<b>C</b>) CPU usage in megabyte on 12 videos using different number of workers.</p> Full article ">Figure 20
<p>Screen captures of mobile data collector application. Students/academic staff use mobile application to record the video-containing-faces of the student. Video then uploaded to server for feature processing.</p> Full article ">Figure 21
<p>A web page for tracking attendance based on the pre added schedule.</p> Full article ">
12 pages, 317 KiB  
Article
A Robust Hybrid Iterative Linear Detector for Massive MIMO Uplink Systems
by Mahmoud A. Albreem, Mohammed H. Alsharif and Sunghwan Kim
Symmetry 2020, 12(2), 306; https://doi.org/10.3390/sym12020306 - 21 Feb 2020
Cited by 9 | Viewed by 3636
Abstract
Fifth-generation (5G) communications system is commercially introduced by several mobile operators where sub-6 GHz bands are the backbone of the 5G networks. A large-scale multiple-input multiple-output (MIMO), or massive MIMO (mMIMO), technology has a major impact to secure high data rate, high spectral [...] Read more.
Fifth-generation (5G) communications system is commercially introduced by several mobile operators where sub-6 GHz bands are the backbone of the 5G networks. A large-scale multiple-input multiple-output (MIMO), or massive MIMO (mMIMO), technology has a major impact to secure high data rate, high spectral efficiency, and quality of service (QoS). It could also have a major role in the beyond-5G systems. A massive number of antennas seek advanced signal processing to detect and equalize the signal. However, optimal detectors, such as the maximum likelihood (ML) and maximum posterior (MAP), are not desirable in implementation due to extremely high complexity. Therefore, sub-optimum solutions have been introduced to obtain and guarantee enough balance between the performance and the computational complexity. In this paper, a robust and joint low complexity detection algorithm is proposed based on the Jacobi (JA) and Gauss–Seidel (GS) methods. In such iterative methods, the performance, complexity, and convergence rate are highly dependent on the initial vector. In this paper, initial solution is proposed by exploiting the benefits of a stair matrix to obtain a fast convergence rate, high performance, and low complexity. Numerical results show that proposed algorithm achieves high accuracy and relieve the computational complexity even when the BS-to-user-antenna ratio (BUAR) is small. Full article
(This article belongs to the Special Issue Information Technologies and Electronics)
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Block diagram of the proposed detector based on the JA and GS methods and a stair matrix.</p> Full article ">Figure 2
<p>Flowchart of the proposed detector based on the JA and GS methods and a stair matrix.</p> Full article ">Figure 3
<p>Performance of the GS, JA, NS, and proposed algorithm at <math display="inline"><semantics> <mrow> <mn>30</mn> <mo>×</mo> <mn>160</mn> </mrow> </semantics></math> mMIMO size and <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>2</mn> </mrow> </semantics></math>.</p> Full article ">Figure 4
<p>Performance of the GS, JA, NS, and proposed algorithm at <math display="inline"><semantics> <mrow> <mn>40</mn> <mo>×</mo> <mn>160</mn> </mrow> </semantics></math> mMIMO size and <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>2</mn> <mo>.</mo> </mrow> </semantics></math></p> Full article ">Figure 5
<p>Performance of the GS, JA, NS, and proposed algorithm at <math display="inline"><semantics> <mrow> <mn>50</mn> <mo>×</mo> <mn>160</mn> </mrow> </semantics></math> mMIMO size and <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>2</mn> </mrow> </semantics></math>.</p> Full article ">Figure 6
<p>Performance of the GS, JA, NS, and proposed algorithm at <math display="inline"><semantics> <mrow> <mn>60</mn> <mo>×</mo> <mn>160</mn> </mrow> </semantics></math> mMIMO size and <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>2</mn> </mrow> </semantics></math>.</p> Full article ">Figure 7
<p>Performance of the GS, JA, NS, and proposed algorithm at <math display="inline"><semantics> <mrow> <mn>60</mn> <mo>×</mo> <mn>160</mn> </mrow> </semantics></math> mMIMO size and <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>3</mn> </mrow> </semantics></math>.</p> Full article ">Figure 8
<p>Performance of the GS, JA, NS, and proposed algorithm at <math display="inline"><semantics> <mrow> <mn>60</mn> <mo>×</mo> <mn>160</mn> </mrow> </semantics></math> mMIMO size and <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>4</mn> </mrow> </semantics></math>.</p> Full article ">Figure 9
<p>A comparison between a detector based on the GS method and the proposed method in 40 mMIMO system to obtain BER = <math display="inline"><semantics> <msup> <mn>10</mn> <mrow> <mo>−</mo> <mn>3</mn> </mrow> </msup> </semantics></math>.</p> Full article ">
23 pages, 1612 KiB  
Article
Decision to Adopt Neuromarketing Techniques for Sustainable Product Marketing: A Fuzzy Decision-Making Approach
by Mehrbakhsh Nilashi, Elaheh Yadegaridehkordi, Sarminah Samad, Abbas Mardani, Ali Ahani, Nahla Aljojo, Nor Shahidayah Razali and Taniza Tajuddin
Symmetry 2020, 12(2), 305; https://doi.org/10.3390/sym12020305 - 21 Feb 2020
Cited by 19 | Viewed by 10147
Abstract
Sustainable products and their marketing have played a crucial role in developing more sustainable consumption patterns and solutions for socio-ecological problems. They have been demonstrated to significantly decrease social consumption problems. Neuromarketing has recently gained considerable popularity and helped companies generate deeper insights [...] Read more.
Sustainable products and their marketing have played a crucial role in developing more sustainable consumption patterns and solutions for socio-ecological problems. They have been demonstrated to significantly decrease social consumption problems. Neuromarketing has recently gained considerable popularity and helped companies generate deeper insights into consumer behavior. It has provided new ways of conceptualizing consumer behavior and decision making. Thus, this research aims to investigate the factors influencing managers’ decisions to adopt neuromarketing techniques in sustainable product marketing using the fuzzy analytic hierarchy process (AHP) approach. Symmetric triangular fuzzy numbers were used to indicate the relative strength of the elements in the hierarchy. Data were collected from the marketing managers of several companies who have experience with sustainable product marketing through online shopping platforms. The results revealed that the accuracy and bias of neuromarketing techniques have been the main critical factors for managers to select neuromarketing in their business for advertising and branding purposes. This research provides important results on the use of neuromarketing techniques for sustainable product marketing, as well as their limitations and implications, and it also presents useful information on the factors impacting business managers’ decision making in adopting neuroscience techniques for sustainable product development and marketing. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>The proposed model for adoption of neuromarketing for sustainable product marketing.</p> Full article ">Figure 2
<p>Final weights of alternatives for sustainable product marketing using neuromarketing.</p> Full article ">Figure 3
<p>Final weights of criteria for sustainable product marketing using neuromarketing.</p> Full article ">
12 pages, 290 KiB  
Article
Recognition and Optimization Algorithms for P5-Free Graphs
by Mihai Talmaciu, Luminiţa Dumitriu, Ioan Şuşnea, Victor Lepin and László Barna Iantovics
Symmetry 2020, 12(2), 304; https://doi.org/10.3390/sym12020304 - 20 Feb 2020
Viewed by 2154
Abstract
The weighted independent set problem on P 5 -free graphs has numerous applications, including data mining and dispatching in railways. The recognition of P 5 -free graphs is executed in polynomial time. Many problems, such as chromatic number and dominating set, are NP-hard [...] Read more.
The weighted independent set problem on P 5 -free graphs has numerous applications, including data mining and dispatching in railways. The recognition of P 5 -free graphs is executed in polynomial time. Many problems, such as chromatic number and dominating set, are NP-hard in the class of P 5 -free graphs. The size of a minimum independent feedback vertex set that belongs to a P 5 -free graph with n vertices can be computed in O ( n 16 ) time. The unweighted problems, clique and clique cover, are NP-complete and the independent set is polynomial. In this work, the P 5 -free graphs using the weak decomposition are characterized, as is the dominating clique, and they are given an O ( n ( n + m ) ) recognition algorithm. Additionally, we calculate directly the clique number and the chromatic number; determine in O ( n ) time, the size of a minimum independent feedback vertex set; and determine in O ( n + m ) time the number of stability, the dominating number and the minimum clique cover. Full article
19 pages, 5582 KiB  
Article
Disdrometer Performance Optimization for Use in Urban Settings Based on the Parameters that Affect the Measurements
by Ferran Mocholí Belenguer, Antonio Martínez-Millana, Antonio Mocholí Salcedo, Víctor Milián Sánchez and María Josefa Palomo Anaya
Symmetry 2020, 12(2), 303; https://doi.org/10.3390/sym12020303 - 20 Feb 2020
Cited by 6 | Viewed by 2720
Abstract
There are currently different types of commercial optical disdrometers to measure the rainfall intensity, of which many are commonly used for monitoring road conditions. Having information about the amount of rain, the composition of the precipitation particles and visibility are essential to avoid [...] Read more.
There are currently different types of commercial optical disdrometers to measure the rainfall intensity, of which many are commonly used for monitoring road conditions. Having information about the amount of rain, the composition of the precipitation particles and visibility are essential to avoid accidents, which requires intelligent systems that warn drivers and redirect traffic. However, few studies related to Intelligent Transport Systems (ITS) have been performed regarding why these devices are not optimized for this type of applications. Therefore, this paper analyzes and evaluates the operating mode of these equipment through their theoretical model, which will allow the design of prototypes of disdrometers with different characteristics. In addition, this model will be implemented in a simulation program, through which an exhaustive study analyzing how the type of precipitation and its intensity affect the measures provided by the model will be conducted. In this way, the results will help optimize its operation to be thus used in urban settings, which will allow obtaining more accurate real-time information, better traffic management, and a reduction in the number of accidents. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Implementation of an optical disdrometer.</p> Full article ">Figure 2
<p>Theoretical relationship between light attenuation and the droplet diameter.</p> Full article ">Figure 3
<p>Effect of the drop oblateness.</p> Full article ">Figure 4
<p>Gamma function of the drop size distribution for different μ values.</p> Full article ">Figure 5
<p>Representation of the surface covered by the passage of a drop through the sensitive volume.</p> Full article ">Figure 6
<p>Signals generated by the passage of the droplets through the sensitive volume for 1 s with a precipitation intensity of 10 mm/h.</p> Full article ">Figure 7
<p>Superposition of several droplets simultaneously passing through the sensitive volume. (<b>A</b>) Signals generated by the passage; (<b>B</b>) A droplet that rubs the sensitive volume.</p> Full article ">Figure 8
<p>PI estimation for stratiform rainfall using the (<b>A</b>) time technique and (<b>B</b>) counting technique.</p> Full article ">Figure 9
<p>PI estimation for convective rainfall using the (<b>A</b>) time technique and (<b>B</b>) counting technique.</p> Full article ">Figure 10
<p>PI estimation errors of the counting and time techniques for different sampling times for (<b>A</b>) stratiform rain and (<b>B</b>) convective rain.</p> Full article ">Figure 10 Cont.
<p>PI estimation errors of the counting and time techniques for different sampling times for (<b>A</b>) stratiform rain and (<b>B</b>) convective rain.</p> Full article ">Figure 11
<p>Estimated PI with 10-bit converters for stratiform rainfall, different precipitation intensities and different wind speeds: (<b>A</b>) time technique and (<b>B</b>) counting technique.</p> Full article ">Figure 12
<p>Estimated PI with 10-bit converters for convective rainfall, different precipitation intensities and different wind speeds: (<b>A</b>) time technique and (<b>B</b>) counting technique.</p> Full article ">Figure 13
<p>Estimated PI with 8-bit converters for stratiform rainfall, different precipitation intensities and different wind speeds: (<b>A</b>) time technique and (<b>B</b>) counting technique.</p> Full article ">Figure 13 Cont.
<p>Estimated PI with 8-bit converters for stratiform rainfall, different precipitation intensities and different wind speeds: (<b>A</b>) time technique and (<b>B</b>) counting technique.</p> Full article ">Figure 14
<p>Estimated PI with 8-bit converters for convective rainfall, different precipitation intensities and different wind speeds: (<b>A</b>) time technique and (<b>B</b>) counting technique.</p> Full article ">
18 pages, 1100 KiB  
Article
A New Integrated Multi-Criteria Decision Making and Multi-Objective Programming Model for Sustainable Supplier Selection and Order Allocation
by Shan-Yong You, Li-Jun Zhang, Xue-Guo Xu and Hu-Chen Liu
Symmetry 2020, 12(2), 302; https://doi.org/10.3390/sym12020302 - 20 Feb 2020
Cited by 30 | Viewed by 3546
Abstract
With the increasing pressure from global competition, manufacturers have realized that sustainable production is significant in supply chain management. Sustainable supplier selection and order allocation (SSS&OA) play a distinct and critical role for organizations to achieve sustainable development and build competitive advantage. In [...] Read more.
With the increasing pressure from global competition, manufacturers have realized that sustainable production is significant in supply chain management. Sustainable supplier selection and order allocation (SSS&OA) play a distinct and critical role for organizations to achieve sustainable development and build competitive advantage. In this paper, we aim to develop a novel SSS&OA model for selecting the most suitable sustainable suppliers and determining the optimal order sizes among them. First, double hierarchy hesitant linguistic term sets (DHHLTSs) are adopted to deal with uncertainty in evaluating the sustainable performance of alternative suppliers. Then, an extended decision field theory is proposed to choose efficient sustainable suppliers dynamically. Considering quantity discount, a multi-objective linear programming (MOLP) model is established to allocate reasonable order quantities among the selected suppliers. Finally, the applicability and effectiveness of the developed model are illustrated through its application in the electronic industry and through a comparative analysis with other methods. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Flowchart of the developed SSS&amp;OA model.</p> Full article ">Figure 2
<p>Ranking results via different methods.</p> Full article ">
21 pages, 5354 KiB  
Article
An Improved Network Traffic Classification Model Based on a Support Vector Machine
by Jie Cao, Da Wang, Zhaoyang Qu, Hongyu Sun, Bin Li and Chin-Ling Chen
Symmetry 2020, 12(2), 301; https://doi.org/10.3390/sym12020301 - 20 Feb 2020
Cited by 23 | Viewed by 4633
Abstract
Network traffic classification based on machine learning is an important branch of pattern recognition in computer science. It is a key technology for dynamic intelligent network management and enhanced network controllability. However, the traffic classification methods still facing severe challenges: The optimal set [...] Read more.
Network traffic classification based on machine learning is an important branch of pattern recognition in computer science. It is a key technology for dynamic intelligent network management and enhanced network controllability. However, the traffic classification methods still facing severe challenges: The optimal set of features is difficult to determine. The classification method is highly dependent on the effective characteristic combination. Meanwhile, it is also important to balance the experience risk and generalization ability of the classifier. In this paper, an improved network traffic classification model based on a support vector machine is proposed. First, a filter-wrapper hybrid feature selection method is proposed to solve the false deletion of combined features caused by a traditional feature selection method. Second, to balance the empirical risk and generalization ability of support vector machine (SVM) traffic classification model, an improved parameter optimization algorithm is proposed. The algorithm can dynamically adjust the quadratic search area, reduce the density of quadratic mesh generation, improve the search efficiency of the algorithm, and prevent the over-fitting while optimizing the parameters. The experiments show that the improved traffic classification model achieves higher classification accuracy, lower dimension and shorter elapsed time and performs significantly better than traditional SVM and the other three typical supervised ML algorithms. Full article
►▼ Show Figures

Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The improved network traffic classification based on SVM.</p> Full article ">Figure 2
<p>Filter-wrapper hybrid feature selection model based on SVM.</p> Full article ">Figure 3
<p>Filter (IG) feature selection process.</p> Full article ">Figure 4
<p>Filter (IG) feature selection process.</p> Full article ">Figure 5
<p>The accuracy of Traffic Classification corresponding to feature subsets.(<b>a</b>) www; (<b>b</b>) Mail; (<b>c</b>) Ftp-control; (<b>d</b>) Ftp-pasv; (<b>e</b>) Attack; (<b>f</b>) P2P; (<b>g</b>) Database; (<b>h</b>) Ftp-data; (<b>i</b>) Multimedia; (<b>j</b>) Services.</p> Full article ">Figure 5 Cont.
<p>The accuracy of Traffic Classification corresponding to feature subsets.(<b>a</b>) www; (<b>b</b>) Mail; (<b>c</b>) Ftp-control; (<b>d</b>) Ftp-pasv; (<b>e</b>) Attack; (<b>f</b>) P2P; (<b>g</b>) Database; (<b>h</b>) Ftp-data; (<b>i</b>) Multimedia; (<b>j</b>) Services.</p> Full article ">Figure 6
<p>Comparison of classification performance before and after Filter-Wrapper feature selection. (<b>a</b>) Accuracy (%); (<b>b</b>) Elapsed time (s); (<b>c</b>) Dimensions.</p> Full article ">Figure 7
<p>Comparison of performance between two-Classification and multi-Classification under different <math display="inline"><semantics> <mrow> <mi>k</mi> <mo>−</mo> <mi>C</mi> <mi>V</mi> <mfenced> <mrow> <mi>k</mi> <mo>=</mo> <mn>3</mn> <mo>,</mo> <mi>k</mi> <mo>=</mo> <mn>10</mn> </mrow> </mfenced> </mrow> </semantics></math>. (<b>a</b>) Elapsed Time (S); (<b>b</b>) Accuracy (%).</p> Full article ">Figure 8
<p>Performance comparison of SVM two-Classification and multi-Classification before and after IGS. (<b>a</b>) Accuracy (%); (<b>b</b>) Elapsed time (S).</p> Full article ">Figure 9
<p>Comparison of five algorithms on data sets with different sample sizes. (<b>a</b>) Accuracy (%) (sample size = 5000); (<b>b</b>) Accuracy (%) (sample size = 24897).</p> Full article ">Figure 10
<p>Comparison of different algorithms on the CAIDA dataset.</p> Full article ">
11 pages, 335 KiB  
Article
Consequences of f(?) Cosmology in Thermal Leptogenesis and Gravitino Late Abundance
by Antonio Capolupo, Salvatore Marco Giampaolo, Gaetano Lambiase and Aniello Quaranta
Symmetry 2020, 12(2), 300; https://doi.org/10.3390/sym12020300 - 19 Feb 2020
Cited by 3 | Viewed by 2416
Abstract
Thermal Leptogenesis and the gravitino problem are reviewed in the framework of non-standard cosmologies. We consider in particular the f ( T ) cosmology, where T is the torsion field. We constrain the parameters space of these cosmological models consistently with thermal Leptogenesis [...] Read more.
Thermal Leptogenesis and the gravitino problem are reviewed in the framework of non-standard cosmologies. We consider in particular the f ( T ) cosmology, where T is the torsion field. We constrain the parameters space of these cosmological models consistently with thermal Leptogenesis scenario (with degenerate mass spectrum of light neutrinos), and we show that they allow to solve the gravitino problem as well. Owing to the similar characteristics to f ( T ) cosmology, we shortly discuss also the case of the shear dominated Universe. Full article
(This article belongs to the Special Issue Geometry, Symmetry and Quantum Field Theory)
17 pages, 486 KiB  
Article
An Approach for Streaming Data Feature Extraction Based on Discrete Cosine Transform and Particle Swarm Optimization
by Özge Aydoğdu and Murat Ekinci
Symmetry 2020, 12(2), 299; https://doi.org/10.3390/sym12020299 - 19 Feb 2020
Cited by 13 | Viewed by 3147
Abstract
Incremental feature extraction algorithms are designed to analyze large-scale data streams. Many of them suffer from high computational cost, time complexity, and data dependency, which adversely affects the processing of the data stream. With this motivation, this paper presents a novel incremental feature [...] Read more.
Incremental feature extraction algorithms are designed to analyze large-scale data streams. Many of them suffer from high computational cost, time complexity, and data dependency, which adversely affects the processing of the data stream. With this motivation, this paper presents a novel incremental feature extraction approach based on the Discrete Cosine Transform (DCT) for the data stream. The proposed approach is separated into initial and sequential phases, and each phase uses a fixed-size windowing technique for processing the current samples. The initial phase is performed only on the first window to construct the initial model as a baseline. In this phase, normalization and DCT are applied to each sample in the window. Subsequently, the efficient feature subset is determined by a particle swarm optimization-based method. With the construction of the initial model, the sequential phase begins. The normalization and DCT processes are likewise applied to each sample. Afterward, the feature subset is selected according to the initial model. Finally, the k-nearest neighbor classifier is employed for classification. The approach is tested on the well-known streaming data sets and compared with state-of-the-art incremental feature extraction algorithms. The experimental studies demonstrate the proposed approach’s success in terms of recognition accuracy and learning time. Full article
(This article belongs to the Special Issue Novel Machine Learning Approaches for Intelligent Big Data 2019)
►▼ Show Figures

Figure 1

Figure 1
<p>Flowchart of the proposed approach.</p> Full article ">Figure 2
<p>Experimental feature selection process.</p> Full article ">Figure 3
<p>The sliding window technique (M1). (<b>a</b>) (<math display="inline"> <semantics> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </semantics> </math>)th data is the current data stream sample, the initial model consists of <span class="html-italic">N</span> data, and <span class="html-italic">N</span> is the sample number of the initial model. (<b>b</b>) The current sample is added at the end of the initial model. (<b>c</b>) The first sample of the initial model is ejected from the model. (<b>d</b>) Updated initial model with the current sample.</p> Full article ">Figure 4
<p>The M3 technique. (<b>a</b>) <math display="inline"> <semantics> <mrow> <mo stretchy="false">(</mo> <mi>N</mi> <mo>+</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </semantics> </math>th data is the current sample, the initial model consists of <span class="html-italic">N</span> data, and <span class="html-italic">N</span> is the sample number of the initial model. (<b>b</b>) The current sample is added to the end of the initial model. (<b>c</b>) <math display="inline"> <semantics> <mrow> <mo stretchy="false">(</mo> <mi>N</mi> <mo>+</mo> <mn>2</mn> <mo stretchy="false">)</mo> </mrow> </semantics> </math>th data comes for processing. (<b>d</b>) <math display="inline"> <semantics> <mrow> <mo stretchy="false">(</mo> <mi>N</mi> <mo>+</mo> <mn>2</mn> <mo stretchy="false">)</mo> </mrow> </semantics> </math>th data is added at the end of the initial model. The sample number of the initial model is increased to <math display="inline"> <semantics> <mrow> <mi>N</mi> <mo>+</mo> <mn>2</mn> </mrow> </semantics> </math>.</p> Full article ">Figure 5
<p>Examining the influence of the interval length for five data sets: (<b>a</b>) ElecNormNews (<b>b</b>), Poker (<b>c</b>), and Forest CovType (<b>d</b>) DS1.</p> Full article ">Figure 6
<p>Comparison of DCT, PSO-DCT, and APSO-DCT: (<b>a</b>) ElecNormNews and (<b>b</b>) Poker.</p> Full article ">
27 pages, 888 KiB  
Article
Fuzzy Decision Support Modeling for Hydrogen Power Plant Selection Based on Single Valued Neutrosophic Sine Trigonometric Aggregation Operators
by Shahzaib Ashraf, Saleem Abdullah, Shouzhen Zeng, Huanhuan Jin and Fazal Ghani
Symmetry 2020, 12(2), 298; https://doi.org/10.3390/sym12020298 - 19 Feb 2020
Cited by 45 | Viewed by 3438
Abstract
In recent decades, there has been a massive growth towards the prime interest of the hydrogen energy industry in automobile transportation fuel. Hydrogen is the most plentiful component and a perfect carrier of energy. Generally, evaluating a suitable hydrogen power plant site is [...] Read more.
In recent decades, there has been a massive growth towards the prime interest of the hydrogen energy industry in automobile transportation fuel. Hydrogen is the most plentiful component and a perfect carrier of energy. Generally, evaluating a suitable hydrogen power plant site is a complex selection of multi-criteria decision-making (MCDM) problem concerning proper location assessment based on numerous essential criteria, the decision-makers expert opinion, and other qualitative/quantitative aspects. This paper presents the novel single-valued neutrosophic (SVN) multi-attribute decision-making method to help decision-makers choose the optimal hydrogen power plant site. At first, novel operating laws based on sine trigonometric function for single-valued neutrosophic sets (SVNSs) are introduced. The well-known sine trigonometry function preserves the periodicity and symmetric in nature about the origin, and therefore it satisfies the decision-maker preferences over the multi-time phase parameters. In conjunction with these properties and laws, we define several new aggregation operators (AOs), called SVN weighted averaging and geometric operators, to aggregate SVNSs. Subsequently, on the basis of the proposed AOs, we introduce decision-making technique for addressing multi-attribute decision-making (MADM) problems and provide a numerical illustration of the hydrogen power plant selection problem for validation. A detailed comparative analysis, including a sensitivity analysis, was carried out to improve the understanding and clarity of the proposed methodologies in view of the existing literature on MADM problems. Full article
(This article belongs to the Special Issue Multi-Criteria Decision Aid methods in fuzzy decision problems – part II)
25 pages, 1409 KiB  
Article
Using Neighborhood Rough Set Theory to Address the Smart Elderly Care in Multi-Level Attributes
by Jining Zhou, Bo Zhang, Runhua Tan, Ming-Lang Tseng, Remen Chun-Wei Lin and Ming K. Lim
Symmetry 2020, 12(2), 297; https://doi.org/10.3390/sym12020297 - 19 Feb 2020
Cited by 6 | Viewed by 2997
Abstract
The neighborhood rough set theory was adopted for attributes reduction and the weight distribution of condition attributes based on the concept of importance level. Smart elderly care coverage rate is low in China. A decisive role in the adoption of smart elderly care [...] Read more.
The neighborhood rough set theory was adopted for attributes reduction and the weight distribution of condition attributes based on the concept of importance level. Smart elderly care coverage rate is low in China. A decisive role in the adoption of smart elderly care is still a problem that needs to be addressed. This study contributes to the adoption of smart elderly care was selected as the decision attribute. The remaining attributes are used as conditional attributes and the multi-level symmetric attribute set for assessing acceptance of smart elderly care. Prior studies are not included smart elderly care adoption attributes in multi-levels; hence, this problem needs to be addressed. The results of this study indicate that the condition attribute of gender has the greatest influence on the decision attribute. The condition attribute of living expenses for smart elderly care has the second largest impact on decision attribute. Children’s support for the elderly decency of the novel elderly care system and the acceptance of non-traditional elderly care methods belong to the primary condition attribute of traditional concept. The result indicates traditional concepts have a certain impact on the adoption of smart elderly care and a condition attribute of residence also has a slight influence on the symmetric decision attribute. The sensitivity analysis shows the insights for uncertainties and provides as a basis for the analysis of the attributes in the smart elderly care service adoption. Full article
►▼ Show Figures

Figure 1

Figure 1
<p>Multi-level attribute set block diagram of acceptance for smart elderly care.</p> Full article ">Figure 2
<p>Flow chart of the importance of conditional attributes of smart elderly care services.</p> Full article ">Figure 3
<p><math display="inline"><semantics> <mrow> <mi>f</mi> <mrow> <mo>(</mo> <mi>λ</mi> <mo>)</mo> </mrow> </mrow> </semantics></math> with different <math display="inline"><semantics> <mi mathvariant="sans-serif">λ</mi> </semantics></math> values.</p> Full article ">Figure 4
<p>Flowchart of calculating the importance of conditional attribute subsets to decision attributes.</p> Full article ">Figure 5
<p>The comparison of the classification precision of the decision attributes and the importance of the condition attributes.</p> Full article ">
9 pages, 416 KiB  
Article
The Properties of a Decile-Based Statistic to Measure Symmetry and Asymmetry
by Mohammad Reza Mahmoudi, Roya Nasirzadeh, Dumitru Baleanu and Kim-Hung Pho
Symmetry 2020, 12(2), 296; https://doi.org/10.3390/sym12020296 - 18 Feb 2020
Cited by 7 | Viewed by 3179
Abstract
This paper studies a simple skewness measure to detect symmetry and asymmetry in samples. The statistic can be obviously applied with only three short central tendencies; i.e., the first and ninth deciles, and the median. The strength of the statistic to find symmetry [...] Read more.
This paper studies a simple skewness measure to detect symmetry and asymmetry in samples. The statistic can be obviously applied with only three short central tendencies; i.e., the first and ninth deciles, and the median. The strength of the statistic to find symmetry and asymmetry is studied by employing numerous Monte Carlo simulations and is compared with some alternative measures by applying some simulation studies. The results show that the performance of this statistic is generally good in the simulation. Full article
(This article belongs to the Special Issue Multibody Systems with Flexible Elements)
►▼ Show Figures

Figure 1

Figure 1
<p>The Q–Q plots versus standard normal distribution. Normal distribution: <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>50</mn> </mrow> </semantics></math> (<b>a</b>), <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>1000</mn> </mrow> </semantics></math> (<b>b</b>). <span class="html-italic">t distribution:</span> <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>50</mn> </mrow> </semantics></math> (<b>c</b>), <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>1000</mn> </mrow> </semantics></math> (<b>d</b>). Uniform distribution: <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>50</mn> </mrow> </semantics></math> (<b>e</b>), <math display="inline"><semantics> <mrow> <mi>n</mi> <mo>=</mo> <mn>1000</mn> <mtext> </mtext> </mrow> </semantics></math>(<b>f</b>).</p> Full article ">
19 pages, 1223 KiB  
Article
Analysis of the Spanish IBEX-35 Companies’ Returns Using Extensions of the Fama and French Factor Models
by Francisco Jareño, María de la O González and Laura Munera
Symmetry 2020, 12(2), 295; https://doi.org/10.3390/sym12020295 - 18 Feb 2020
Cited by 5 | Viewed by 3367
Abstract
This paper studies in depth the sensitivity of Spanish companies’ returns to changes in several risk factors between January 2000 and December 2018 using the quantile regression approach. Concretely, this research applies extensions of the Fama and French three- and five-factor models (1993 [...] Read more.
This paper studies in depth the sensitivity of Spanish companies’ returns to changes in several risk factors between January 2000 and December 2018 using the quantile regression approach. Concretely, this research applies extensions of the Fama and French three- and five-factor models (1993 and 2015), according to González and Jareño (2019), adding relevant explanatory factors, such as nominal interest rates, the Carhart (1997) risk factor for momentum and for momentum reversal and the Pastor and Stambaugh (2003) traded liquidity factor. Additionally, for robustness, this paper splits the entire sample period into three sub-sample periods (pre-crisis, crisis and post-crisis) to analyse the results according to the economic cycle. The main conclusions of this paper are fourfold: First, these two models have the greatest explanatory power in the extreme quantiles of the return distribution (0.1 and 0.9) and more specifically in the lowest quantile 0.1. Second, the second model, based on the Fama and French five-factor model, shows the highest explanatory power not only in the full period but also in the three sub-periods. Third, the bank BBVA is the company that shows the highest sensitivity to changes in the explanatory factors in most periods because its adjusted R2 is the highest. Fourth, the stage of the economy with the highest explanatory power is the crisis subperiod. Thus, the final conclusion of this paper is that the second model explains best variations in Spanish companies’ returns in crisis stages and low quantiles. Full article
(This article belongs to the Special Issue Application of symmetry analysis to mathematical biology, engineering, and finance)
►▼ Show Figures

Figure 1

Figure 1
<p>Components of the Spanish IBEX-35 index in 2019: company (code) (<span class="html-italic">x</span>-axis) and weight (<span class="html-italic">y</span>-axis). Source: BME (Spanish Stock Exchanges and Markets).</p> Full article ">Figure 2
<p>Adjusted <span class="html-italic">R</span><sup>2</sup> by quantile for Models A (dark) and B (light): whole sample period. (<b>A</b>): Mean Adj. <span class="html-italic">R</span><sup>2</sup>. (<b>B</b>): Maximum Adj. <span class="html-italic">R</span><sup>2</sup>. Source: Own elaboration from Eviews data.</p> Full article ">Figure 3
<p>Adjusted <span class="html-italic">R</span><sup>2</sup> by quantile for Models A (dark) and B (light): precrisis subperiod. (<b>A</b>): Mean Adj. <span class="html-italic">R</span><sup>2</sup>. (<b>B</b>): Maximum Adj. <span class="html-italic">R</span><sup>2</sup>. Source: Own elaboration from Eviews data.</p> Full article ">Figure 4
<p>Adjusted <span class="html-italic">R</span><sup>2</sup> by quantile for Models A (dark) and B (light): crisis subperiod. (<b>A</b>): Mean Adj. <span class="html-italic">R</span><sup>2</sup>. (<b>B</b>): Maximum Adj. <span class="html-italic">R</span><sup>2</sup>. Source: Own elaboration from Eviews data.</p> Full article ">Figure 5
<p>Adjusted <span class="html-italic">R</span><sup>2</sup> by quantile for Models A (dark) and B (light): postcrisis subperiod. (<b>A</b>): Mean Adj. <span class="html-italic">R</span><sup>2</sup>. (<b>B</b>): Maximum Adj. <span class="html-italic">R</span><sup>2</sup>. Source: Own elaboration from Eviews data.</p> Full article ">
Show export options expand_more Show export options expand_less
Select all
Export citation of selected articles as:
 
Displaying articles 1-140
Previous Issue
Next Issue
Back to TopTop