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Symmetry, Volume 11, Issue 8 (August 2019)

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Cover Story (view full-size image) We find that the $H_0$ tension can be significantly alleviated, or even removed, if we account for [...] Read more.
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Open AccessArticle
Evaluation of Rolling Bearing Performance Degradation Using Wavelet Packet Energy Entropy and RBF Neural Network
Symmetry 2019, 11(8), 1064; https://doi.org/10.3390/sym11081064
Received: 26 June 2019 / Revised: 24 July 2019 / Accepted: 19 August 2019 / Published: 20 August 2019
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Abstract
Rolling bearings are the most important parts in rotating machinery, and one of the most vulnerable parts to failure. The rolling bearing is a cyclic symmetrical structure that is stable under normal operating conditions. However, when the rolling bearing fails, its symmetry is [...] Read more.
Rolling bearings are the most important parts in rotating machinery, and one of the most vulnerable parts to failure. The rolling bearing is a cyclic symmetrical structure that is stable under normal operating conditions. However, when the rolling bearing fails, its symmetry is destroyed, resulting in unstable performance and causing major accidents. If the performance of rolling bearings can be monitored and evaluated in real time, maintenance strategies can be implemented promptly. In this paper, by using wavelet packet energy entropy (WPEE), the early fault-free features of bearing and the failure samples of similar bearings are decomposed firstly, and the energy value is extracted as the original feature, simultaneously. Secondly, a radial basis function (RBF) neural network model is established by using early fault-free features and similar bearing failure characteristics. The bearing full-life data characteristics of the extracted features are added into the RBF model in an iterative manner to obtain performance degradation Indicator. Boxplot was introduced as an adaptive threshold method to determine the failure threshold. Finally, the results are verified by empirical mode decomposition and Hilbert envelope demodulation. A bearing accelerated life experiment is performed to validate the feasibility and validity of the proposed method. The experimental results show that the method can diagnose early fault points in time and evaluate the degree of bearing degradation, which is of great significance for industrial practical applications. Full article
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Open AccessArticle
Forecasting for Ultra-Short-Term Electric Power Load Based on Integrated Artificial Neural Networks
Symmetry 2019, 11(8), 1063; https://doi.org/10.3390/sym11081063
Received: 25 July 2019 / Revised: 9 August 2019 / Accepted: 14 August 2019 / Published: 20 August 2019
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Abstract
Energy efficiency and renewable energy are the two main research topics for sustainable energy. In the past ten years, countries around the world have invested a lot of manpower into new energy research. However, in addition to new energy development, energy efficiency technologies [...] Read more.
Energy efficiency and renewable energy are the two main research topics for sustainable energy. In the past ten years, countries around the world have invested a lot of manpower into new energy research. However, in addition to new energy development, energy efficiency technologies need to be emphasized to promote production efficiency and reduce environmental pollution. In order to improve power production efficiency, an integrated solution regarding the issue of electric power load forecasting was proposed in this study. The solution proposed was to, in combination with persistence and search algorithms, establish a new integrated ultra-short-term electric power load forecasting method based on the adaptive-network-based fuzzy inference system (ANFIS) and back-propagation neural network (BPN), which can be applied in forecasting electric power load in Taiwan. The research methodology used in this paper was mainly to acquire and process the all-day electric power load data of Taiwan Power and execute preliminary forecasting values of the electric power load by applying ANFIS, BPN and persistence. The preliminary forecasting values of the electric power load obtained therefrom were called suboptimal solutions and finally the optimal weighted value was determined by applying a search algorithm through integrating the above three methods by weighting. In this paper, the optimal electric power load value was forecasted based on the weighted value obtained therefrom. It was proven through experimental results that the solution proposed in this paper can be used to accurately forecast electric power load, with a minimal error. Full article
(This article belongs to the Special Issue Selected Papers from IIKII 2019 conferences in Symmetry)
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Open AccessArticle
Image Enhancement Using Modified Histogram and Log-Exp Transformation
Symmetry 2019, 11(8), 1062; https://doi.org/10.3390/sym11081062
Received: 11 July 2019 / Revised: 13 August 2019 / Accepted: 13 August 2019 / Published: 20 August 2019
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Abstract
An effective method to enhance the contrast of digital images is proposed in this paper. A histogram function is developed to make the histogram curve smoother, which can be used to avoid the loss of information in the processed image. Besides the histogram [...] Read more.
An effective method to enhance the contrast of digital images is proposed in this paper. A histogram function is developed to make the histogram curve smoother, which can be used to avoid the loss of information in the processed image. Besides the histogram function, an adaptive gamma correction for the histogram is proposed to stretch the brightness contrast. Moreover, the log-exp transformation strategy is presented to progressively increase the low intensity while suppressing the decrement of the high intensity. In order to further widen the dynamic range of the image, the nonlinear normalization transformation is put forward to make the output image more natural and clearer. In the experiment on non-uniform illumination images, the average contrast per pixel (CPP), root mean square (RMS), and discrete entropy (DE) metrics of the developed approach are shown to be superior to selected state-of-the-art methods. Full article
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Open AccessArticle
Mei Symmetry and Invariants of Quasi-Fractional Dynamical Systems with Non-Standard Lagrangians
Symmetry 2019, 11(8), 1061; https://doi.org/10.3390/sym11081061
Received: 15 July 2019 / Revised: 14 August 2019 / Accepted: 15 August 2019 / Published: 18 August 2019
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Abstract
Non-standard Lagrangians play an important role in the systems of non-conservative dynamics or nonlinear differential equations, quantum field theories, etc. This paper deals with quasi-fractional dynamical systems from exponential non-standard Lagrangians and power-law non-standard Lagrangians. Firstly, the definition, criterion, and corresponding new conserved [...] Read more.
Non-standard Lagrangians play an important role in the systems of non-conservative dynamics or nonlinear differential equations, quantum field theories, etc. This paper deals with quasi-fractional dynamical systems from exponential non-standard Lagrangians and power-law non-standard Lagrangians. Firstly, the definition, criterion, and corresponding new conserved quantity of Mei symmetry in this system are presented and studied. Secondly, considering that a small disturbance is applied on the system, the differential equations of the disturbed motion are established, the definition of Mei symmetry and corresponding criterion are given, and the new adiabatic invariants led by Mei symmetry are proposed and proved. Examples also show the validity of the results. Full article
(This article belongs to the Special Issue Symmetry in Complex Systems)
Open AccessArticle
Refinement Asymptotic Formulas of Eigenvalues and Eigenfunctions of a Fourth Order Linear Differential Operator with Transmission Condition and Discontinuous Weight Function
Symmetry 2019, 11(8), 1060; https://doi.org/10.3390/sym11081060
Received: 18 July 2019 / Revised: 14 August 2019 / Accepted: 16 August 2019 / Published: 17 August 2019
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Abstract
In this paper, we promote the refinement method for estimating asymptotic expression of the fundamental solutions of a fourth order linear differential equation with discontinuous weight function and transmission conditions. These refinement solutions utilize more accurate asymptotic formulas for the eigenvalues and eigenfunctions [...] Read more.
In this paper, we promote the refinement method for estimating asymptotic expression of the fundamental solutions of a fourth order linear differential equation with discontinuous weight function and transmission conditions. These refinement solutions utilize more accurate asymptotic formulas for the eigenvalues and eigenfunctions for the problem. Full article
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Open AccessArticle
Goal Recognition Control under Network Interdiction Using a Privacy Information Metric
Symmetry 2019, 11(8), 1059; https://doi.org/10.3390/sym11081059
Received: 4 July 2019 / Revised: 26 July 2019 / Accepted: 13 August 2019 / Published: 17 August 2019
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Abstract
Goal recognition (GR) is a method of inferring the goals of other agents, which enables humans or AI agents to proactively make response plans. Goal recognition design (GRD) has been proposed to deliberately redesign the underlying environment to accelerate goal recognition. Along with [...] Read more.
Goal recognition (GR) is a method of inferring the goals of other agents, which enables humans or AI agents to proactively make response plans. Goal recognition design (GRD) has been proposed to deliberately redesign the underlying environment to accelerate goal recognition. Along with the GR and GRD problems, in this paper, we start by introducing the goal recognition control (GRC) problem under network interdiction, which focuses on controlling the goal recognition process. When the observer attempts to facilitate the explainability of the actor’s behavior and accelerate goal recognition by reducing the uncertainty, the actor wants to minimize the privacy information leakage by manipulating the asymmetric information and delay the goal recognition process. Then, the GRC under network interdiction is formulated as one static Stackelberg game, where the observer obtains asymmetric information about the actor’s intended goal and proactively interdicts the edges of the network with a bounded resource. The privacy leakage of the actor’s actions about the real goals is quantified by a min-entropy information metric and this privacy information metric is associated with the goal uncertainty. Next in importance, we define the privacy information metric based GRC under network interdiction (InfoGRC) and the information metric based GRC under threshold network interdiction (InfoGRCT). After dual reformulating, the InfoGRC and InfoGRCT as bi-level mixed-integer programming problems, one Benders decomposition-based approach is adopted to optimize the observer’s optimal interdiction resource allocation and the actor’s cost-optimal path-planning. Finally, some experimental evaluations are conducted to demonstrate the effectiveness of the InfoGRC and InfoGRCT models in the task of controlling the goal recognition process. Full article
(This article belongs to the Special Issue Protection of Graphs)
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Open AccessArticle
Generalization of Maximizing Deviation and TOPSIS Method for MADM in Simplified Neutrosophic Hesitant Fuzzy Environment
Symmetry 2019, 11(8), 1058; https://doi.org/10.3390/sym11081058
Received: 25 June 2019 / Revised: 26 July 2019 / Accepted: 1 August 2019 / Published: 17 August 2019
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Abstract
With the development of the social economy and enlarged volume of information, the application of multiple-attribute decision-making (MADM) has become increasingly complex, uncertain, and obscure. As a further generalization of hesitant fuzzy set (HFS), simplified neutrosophic hesitant fuzzy set (SNHFS) is an efficient [...] Read more.
With the development of the social economy and enlarged volume of information, the application of multiple-attribute decision-making (MADM) has become increasingly complex, uncertain, and obscure. As a further generalization of hesitant fuzzy set (HFS), simplified neutrosophic hesitant fuzzy set (SNHFS) is an efficient tool to process the vague information and contains the ideas of a single-valued neutrosophic hesitant fuzzy set (SVNHFS) and an interval neutrosophic hesitant fuzzy set (INHFS). In this paper, we propose a decision-making approach based on the maximizing deviation method and TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) to solve the MADM problems, in which the attribute weight information is incomplete, and the decision information is expressed in simplified neutrosophic hesitant fuzzy elements. Firstly, we inaugurate an optimization model on the basis of maximizing deviation method, which is useful to determine the attribute weights. Secondly, using the idea of the TOPSIS, we determine the relative closeness coefficient of each alternative and based on which we rank the considered alternatives to select the optimal one(s). Finally, we use a numerical example to show the detailed implementation procedure and effectiveness of our method in solving MADM problems under simplified neutrosophic hesitant fuzzy environment. Full article
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Open AccessArticle
Research on Safety Regulation of Chemical Enterprise under Third-Party Mechanism: An Evolutionary Approach
Symmetry 2019, 11(8), 1057; https://doi.org/10.3390/sym11081057
Received: 21 July 2019 / Revised: 12 August 2019 / Accepted: 15 August 2019 / Published: 16 August 2019
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Abstract
In recent years, China’s chemical industry has incurred frequent safety accidents which seriously impact the social environment and public safety. Traditional approaches have reached a bottleneck due to a lack of relevant professionals in the government regulation of chemical enterprise safety production. Thus, [...] Read more.
In recent years, China’s chemical industry has incurred frequent safety accidents which seriously impact the social environment and public safety. Traditional approaches have reached a bottleneck due to a lack of relevant professionals in the government regulation of chemical enterprise safety production. Thus, a new safety regulation mechanism should be conducted. In this paper, we constructed an evolutionary game model of chemical industry safety regulation based on limited rationality, and the influence of main parameters on the equilibrium evolution process is studied by system dynamics simulation. The results show that government regulation authorities play a leading role in the process of chemical industry safety regulation and increasing punishment will help to achieve an evolutionary stable strategy (ESS). What is more, the feasibility and effectiveness of the third-party regulation service mechanism are verified, and the market access threshold of third-party regulation service needs to be improved to stop the occurrence of rent-seeking activities in the regulatory process. In summary, the introduction of third-party regulation service entities to the chemical industry safety regulation process has far-reaching implications for promoting the healthy development of China’s chemical industry. Full article
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Open AccessArticle
Symmetry Analysis of an Interest Rate Derivatives PDE Model in Financial Mathematics
Symmetry 2019, 11(8), 1056; https://doi.org/10.3390/sym11081056
Received: 23 July 2019 / Revised: 8 August 2019 / Accepted: 12 August 2019 / Published: 16 August 2019
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Abstract
We perform Lie symmetry analysis to a zero-coupon bond pricing equation whose price evolution is described in terms of a partial differential equation (PDE). As a result, using the computer software package SYM, run in conjunction with Mathematica, a new family of Lie [...] Read more.
We perform Lie symmetry analysis to a zero-coupon bond pricing equation whose price evolution is described in terms of a partial differential equation (PDE). As a result, using the computer software package SYM, run in conjunction with Mathematica, a new family of Lie symmetry group and generators of the aforementioned pricing equation are derived. We furthermore compute the exact invariant solutions which constitute the pricing models for the bond by making use of the derived infinitesimal generators and the associated similarity reduction equations. Using known solutions, we again compute more solutions via group point transformations. Full article
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Open AccessArticle
Forecasting Efficient Risk/Return Frontier for Equity Risk with a KTAP Approach—A Case Study in Milan Stock Exchange
Symmetry 2019, 11(8), 1055; https://doi.org/10.3390/sym11081055
Received: 1 August 2019 / Revised: 13 August 2019 / Accepted: 14 August 2019 / Published: 16 August 2019
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Abstract
We introduce and discuss a dynamics of interaction of risky assets in a portfolio by resorting to methods of statistical mechanics developed to model the evolution of systems whose microscopic state may be augmented by variables which are not mechanical. Statistical methods are [...] Read more.
We introduce and discuss a dynamics of interaction of risky assets in a portfolio by resorting to methods of statistical mechanics developed to model the evolution of systems whose microscopic state may be augmented by variables which are not mechanical. Statistical methods are applied in the present paper in order to forecast the dynamics of risk/return efficient frontier for equity risk. Specifically, we adopt the methodologies of the kinetic theory for active particles (KTAP) with stochastic game-type interactions and apply the proposed model to a case study analyzing a subset of stocks traded in Milan Stock Exchange. In particular, we evaluate the efficient risk/return frontier within the mean/variance portfolio optimization theory for 13 principal components of the Milan Stock Exchange and apply the proposed kinetic model to forecast its short-term evolution (within one year). The model has the aim to pave the way to many different research perspectives and applications discussed eventually in the paper. In particular, the case of efficient frontier obtained by minimizing the Conditional Value-at-Risk (CVaR) is introduced and a preliminary result is proposed. Full article
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Open AccessArticle
An Efficient Class of Weighted-Newton Multiple Root Solvers with Seventh Order Convergence
Symmetry 2019, 11(8), 1054; https://doi.org/10.3390/sym11081054
Received: 27 June 2019 / Revised: 7 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
In this work, we construct a family of seventh order iterative methods for finding multiple roots of a nonlinear function. The scheme consists of three steps, of which the first is Newton’s step and last two are the weighted-Newton steps. Hence, the name [...] Read more.
In this work, we construct a family of seventh order iterative methods for finding multiple roots of a nonlinear function. The scheme consists of three steps, of which the first is Newton’s step and last two are the weighted-Newton steps. Hence, the name of the scheme is ‘weighted-Newton methods’. Theoretical results are studied exhaustively along with the main theorem describing convergence analysis. Stability and convergence domain of the proposed class are also demonstrated by means of using a graphical technique, namely, basins of attraction. Boundaries of these basins are fractal like shapes through which basins are symmetric. Efficacy is demonstrated through numerical experimentation on variety of different functions that illustrates good convergence behavior. Moreover, the theoretical result concerning computational efficiency is verified by computing the elapsed CPU time. The overall comparison of numerical results including accuracy and CPU-time shows that the new methods are strong competitors for the existing methods. Full article
(This article belongs to the Special Issue Symmetry and Complexity 2019)
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Open AccessArticle
A New Strategy for Improving the Tracking Performance of Magnetic Levitation System in Maglev Train
Symmetry 2019, 11(8), 1053; https://doi.org/10.3390/sym11081053
Received: 18 July 2019 / Revised: 9 August 2019 / Accepted: 13 August 2019 / Published: 16 August 2019
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Abstract
The maglev train is a whole new method of transportation without wheels, consisting of 20 groups of symmetry suspension units. The magnetic levitation system plays a major role in suspending the maglev train stably and following the track quickly with the desired gap. [...] Read more.
The maglev train is a whole new method of transportation without wheels, consisting of 20 groups of symmetry suspension units. The magnetic levitation system plays a major role in suspending the maglev train stably and following the track quickly with the desired gap. However, vertical track irregularity in the maglev train line has a dreadful effect on the tracking performance of the magnetic levitation system. The investigations carried out by our team have revealed that the fluctuation of the suspension gap becomes more and more serious with increases in running speed. In this paper, a mathematical model with consideration of vertical track irregularity is established. In order to overcome and suppress the fluctuation of the suspension gap, we propose a new strategy which includes installing an accelerometer on the electromagnet to address this problem. This strategy has already been successfully implemented and applied to the suspension controller for a magnetic levitation system in the Changsha maglev express. Real operation data indicates the tracking performance of the magnetic levitation system was obviously improved. Full article
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Open AccessArticle
Geodesic Chord Property and Hypersurfaces of Space Forms
Symmetry 2019, 11(8), 1052; https://doi.org/10.3390/sym11081052
Received: 22 July 2019 / Revised: 13 August 2019 / Accepted: 14 August 2019 / Published: 16 August 2019
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Abstract
In the Euclidean space En, hyperplanes, hyperspheres and hypercylinders are the only isoparametric hypersurfaces. These hypersurfaces are also the only ones with chord property, that is, the chord connecting two points on them meets the hypersurfaces at the same angle at [...] Read more.
In the Euclidean space E n , hyperplanes, hyperspheres and hypercylinders are the only isoparametric hypersurfaces. These hypersurfaces are also the only ones with chord property, that is, the chord connecting two points on them meets the hypersurfaces at the same angle at the two points. In this paper, we investigate hypersurfaces in nonflat space forms with the so-called geodesic chord property and classify such hypersurfaces completely. Full article
(This article belongs to the Special Issue Geometry of Submanifolds and Homogeneous Spaces)
Open AccessArticle
Retardant Effects of Collapsing Dynamics of a Laser-Induced Cavitation Bubble Near a Solid Wall
Symmetry 2019, 11(8), 1051; https://doi.org/10.3390/sym11081051
Received: 24 July 2019 / Revised: 8 August 2019 / Accepted: 13 August 2019 / Published: 15 August 2019
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Abstract
In the present paper, the dynamic behavior of cavitation bubbles near a wall is experimentally investigated with a focus on the retardant effects of the wall on the collapsing dynamics of the bubble. In the present experiments, a cavitation bubble is generated by [...] Read more.
In the present paper, the dynamic behavior of cavitation bubbles near a wall is experimentally investigated with a focus on the retardant effects of the wall on the collapsing dynamics of the bubble. In the present experiments, a cavitation bubble is generated by a focused laser beam with its behavior recorded through high-speed photography. During the data analysis, the influences of non-dimensional bubble–wall distance on the bubble collapsing dynamics are qualitatively and quantitatively investigated in terms of the interface evolution, the velocities of the poles, and the movement of the bubble centroid. Our results reveal that the presence of the wall could significantly affect the collapsing characteristics, leading to a dramatic difference between the moving velocities of interfaces near and away from the wall. With the decrease of the bubble–wall distance, the effects will be gradually strengthened with a rapid movement of the bubble centroid during the final collapse. Finally, a physical interpretation of the phenomenon is given based on the bubble theory, together with a rough estimation of the induced water hammer pressure by the bubble collapse. Full article
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Open AccessArticle
Dynamic Response of Zener-Modelled Linearly Viscoelastic Systems under Harmonic Excitation
Symmetry 2019, 11(8), 1050; https://doi.org/10.3390/sym11081050
Received: 27 June 2019 / Revised: 7 August 2019 / Accepted: 10 August 2019 / Published: 15 August 2019
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Abstract
A comprehensive investigation, including analytical modelling, numerical analysis and experimental tests, has been carried out on many linear viscoelastic systems and structures. This approach is the result of research conducted by two research institutes, ICECON and INCERC Bucharest, from Romania. Thus, analyses were [...] Read more.
A comprehensive investigation, including analytical modelling, numerical analysis and experimental tests, has been carried out on many linear viscoelastic systems and structures. This approach is the result of research conducted by two research institutes, ICECON and INCERC Bucharest, from Romania. Thus, analyses were performed on the dynamic behaviour of composite viscoelastic materials, anti-vibration viscoelastic systems made of discrete physical devices, road structures consisting of layers of natural soil with mineral aggregates and asphalt mixtures, and mixed mechanic insulation systems for industrial vibrations formed of elastic and viscous devices. The objectives pursued were as follows: (a) providing a mass dosage of the mixture of earth (clay, sand, mineral aggregates, water, and stabilizer) in five variants; (b) carrying out a test run with a Bomag vibratory roller with variable vibration parameters; (c) Experimental evaluation of the vibration parameters and the force transmitted to the ground, correlated with the determination of the compaction layer; (d) use of methods of analysis for physic-mechanical and geotechnical parameters; (e) rheological and numerical modeling based on Zener schematics, so the consistency and veracity of the experimental data with the numerical simulation can be determined. Finally, a study is presented for a test track, where experimental and correlated input and response data are determined to validate the rheological model with a high loading rate. Full article
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Open AccessArticle
An Improved Butterfly Optimization Algorithm for Engineering Design Problems Using the Cross-Entropy Method
Symmetry 2019, 11(8), 1049; https://doi.org/10.3390/sym11081049
Received: 4 July 2019 / Revised: 9 August 2019 / Accepted: 9 August 2019 / Published: 14 August 2019
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Abstract
Engineering design optimization in real life is a challenging global optimization problem, and many meta-heuristic algorithms have been proposed to obtain the global best solutions. An excellent meta-heuristic algorithm has two symmetric search capabilities: local search and global search. In this paper, an [...] Read more.
Engineering design optimization in real life is a challenging global optimization problem, and many meta-heuristic algorithms have been proposed to obtain the global best solutions. An excellent meta-heuristic algorithm has two symmetric search capabilities: local search and global search. In this paper, an improved Butterfly Optimization Algorithm (BOA) is developed by embedding the cross-entropy (CE) method into the original BOA. Based on a co-evolution technique, this new method achieves a proper balance between exploration and exploitation to enhance its global search capability, and effectively avoid it falling into a local optimum. The performance of the proposed approach was evaluated on 19 well-known benchmark test functions and three classical engineering design problems. The results of the test functions show that the proposed algorithm can provide very competitive results in terms of improved exploration, local optima avoidance, exploitation, and convergence rate. The results of the engineering problems prove that the new approach is applicable to challenging problems with constrained and unknown search spaces. Full article
(This article belongs to the Special Issue Symmetry in Mechanical Engineering)
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Open AccessArticle
Docking of Polyethylenimines Derivatives on Cube Rhombellane Functionalized Homeomorphs
Symmetry 2019, 11(8), 1048; https://doi.org/10.3390/sym11081048
Received: 22 July 2019 / Revised: 6 August 2019 / Accepted: 7 August 2019 / Published: 14 August 2019
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Abstract
Nowadays, in the world of science, an important goal is to create new nanostructures that may act as potential drug carriers. Among different, real or hypothetical, polymeric networks, rhombellanes are very promising and, therefore, attempts were made to deposit polyethylenimines as possible nano-drug [...] Read more.
Nowadays, in the world of science, an important goal is to create new nanostructures that may act as potential drug carriers. Among different, real or hypothetical, polymeric networks, rhombellanes are very promising and, therefore, attempts were made to deposit polyethylenimines as possible nano-drug complexes on the cube rhombellane homeomorphs surface. For the search of ligand–fullerene interactions, was used AutoDockVina software. As a reference structure, the fullerene C60 was used. After the docking procedure, the ligands–fullerenes interactions were tested. The important factor determining the mutual affinity of the tested ligands and nanocarriers is the symmetry of the analyzed nanostructures. Here, this feature has the influence on the distribution of such groups like donors and acceptors of hydrogen bonds on the surface of nanoparticles. We calculated the best binding affinities of ligands, values of binding constants and differences relative to C60 molecules. The best binding efficiency was found for linear ligands. It was also found that the shorter the molecule, the better the binding performance, the more the particle grows and the lower the yield. Small structures of ligands react easily with small structures of nanoparticles. The highest positive percentage deviations were obtained for ligand–fullerene complexes showing the highest binding energy values. Detailed analysis of structural properties after docking showed that the values of affinity of the studied indolizine ligands to the rhombellanes surface are correlated with the strength/length of hydrogen bonds formed between them. Full article
(This article belongs to the Special Issue Applied Designs in Chemical Structures with High Symmetry)
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Open AccessArticle
On Z -Invariant Self-Adjoint Extensions of the Laplacian on Quantum Circuits
Symmetry 2019, 11(8), 1047; https://doi.org/10.3390/sym11081047
Received: 16 July 2019 / Revised: 6 August 2019 / Accepted: 10 August 2019 / Published: 14 August 2019
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Abstract
An analysis of the invariance properties of self-adjoint extensions of symmetric operators under the action of a group of symmetries is presented. For a given group G, criteria for the existence of G-invariant self-adjoint extensions of the Laplace–Beltrami operator over a [...] Read more.
An analysis of the invariance properties of self-adjoint extensions of symmetric operators under the action of a group of symmetries is presented. For a given group G, criteria for the existence of G-invariant self-adjoint extensions of the Laplace–Beltrami operator over a Riemannian manifold are illustrated and critically revisited. These criteria are employed for characterising self-adjoint extensions of the Laplace–Beltrami operator on an infinite set of intervals, Ω , constituting a quantum circuit, which are invariant under a given action of the group Z . A study of the different unitary representations of the group Z on the space of square integrable functions on Ω is performed and the corresponding Z -invariant self-adjoint extensions of the Laplace–Beltrami operator are introduced. The study and characterisation of the invariance properties allows for the determination of the spectrum and generalised eigenfunctions in particular examples. Full article
(This article belongs to the Special Issue New trends on Symmetry and Topology in Quantum Mechanics)
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Open AccessArticle
Degenerate Stirling Polynomials of the Second Kind and Some Applications
Symmetry 2019, 11(8), 1046; https://doi.org/10.3390/sym11081046
Received: 20 July 2019 / Revised: 10 August 2019 / Accepted: 13 August 2019 / Published: 14 August 2019
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Abstract
Recently, the degenerate λ-Stirling polynomials of the second kind were introduced and investigated for their properties and relations. In this paper, we continue to study the degenerate λ-Stirling polynomials as well as the r-truncated degenerate λ-Stirling polynomials of the [...] Read more.
Recently, the degenerate λ -Stirling polynomials of the second kind were introduced and investigated for their properties and relations. In this paper, we continue to study the degenerate λ -Stirling polynomials as well as the r-truncated degenerate λ -Stirling polynomials of the second kind which are derived from generating functions and Newton’s formula. We derive recurrence relations and various expressions for them. Regarding applications, we show that both the degenerate λ -Stirling polynomials of the second and the r-truncated degenerate λ -Stirling polynomials of the second kind appear in the expressions of the probability distributions of appropriate random variables. Full article
Open AccessArticle
Overview of High Energy String Scattering Amplitudes and Symmetries of String Theory
Symmetry 2019, 11(8), 1045; https://doi.org/10.3390/sym11081045
Received: 18 June 2019 / Revised: 15 July 2019 / Accepted: 2 August 2019 / Published: 13 August 2019
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Abstract
In this paper, we studied symmetries of string scattering amplitudes in the high energy limits of both the fixed angle or Gross regime (GR) and the fixed momentum transfer or Regge regime (RR). We calculated high energy string scattering amplitudes (SSA) at arbitrary [...] Read more.
In this paper, we studied symmetries of string scattering amplitudes in the high energy limits of both the fixed angle or Gross regime (GR) and the fixed momentum transfer or Regge regime (RR). We calculated high energy string scattering amplitudes (SSA) at arbitrary mass levels for both regimes. We discovered the infinite linear relations among fixed angle string amplitudes and the ifinite recurrence relations among Regge string amplitudes. The linear relations we obtained in the GR corrected the saddle point calculations by Gross, Gross and Mende. In addition, for the high energy closed string scatterings, our results differ from theirs by an oscillating prefactor which was crucial to recover the KLT relation valid for all energies. We showed that all the high energy string amplitudes can be solved using the linear or recurrence relations, so that all the string amplitudes can be expressed in terms of a single string amplitude. We further found that, at each mass level, the ratios among the fixed angle amplitudes can be extracted from the Regge string scattering amplitudes. Finally, we reviewed the recent developments on the discovery of infinite number of recurrence relations valid for all energies among Lauricella SSA. The symmetries or relations among SSA at various limits obtained previously can be exactly reproduced. It leads us to argue that the known S L ( K + 3 , C ) dynamical symmetry of the Lauricella function may be crucial to probe spacetime symmetry of string theory. Full article
Open AccessArticle
Testing New Methods for Boarding a Partially Occupied Airplane Using Apron Buses
Symmetry 2019, 11(8), 1044; https://doi.org/10.3390/sym11081044
Received: 30 July 2019 / Revised: 11 August 2019 / Accepted: 12 August 2019 / Published: 13 August 2019
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Abstract
The use of apron buses has become a common practice at many European airports. Previous studies related to airplane boarding rarely apply when apron buses are used, leaving airlines with no well-researched option except to use the random boarding method. In this paper, [...] Read more.
The use of apron buses has become a common practice at many European airports. Previous studies related to airplane boarding rarely apply when apron buses are used, leaving airlines with no well-researched option except to use the random boarding method. In this paper, we test the time to complete boarding a two-door airplane using various boarding methods with two apron buses. These methods were inspired by the classical outside-in, back-to-front, and reverse-pyramid methods considering the limited number of boarding groups corresponding to the limited number of apron buses used for transporting passengers from the terminal to the aircraft. Unlike earlier publications, we test these methods under partial aircraft occupancy. Furthermore, we test the boarding methods under conditions involving: different passenger occupancy rates, different luggage situations, and with two types of seating assignments—random and based upon passenger seating preferences—by considering the advantages brought by the symmetric layout of the aircraft. Experimental results indicate that the best performing method can reduce the boarding time by up to 38.6% compared to the time resulting from the random boarding method. When the airplane is partially occupied, the best performing methods are reverse pyramid–A, hybrid–A, and hybrid–B, all with similar performances. Full article
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Open AccessArticle
Does Functional Lateralization in Birds Have any Implications for Their Welfare?
Symmetry 2019, 11(8), 1043; https://doi.org/10.3390/sym11081043
Received: 29 July 2019 / Revised: 5 August 2019 / Accepted: 9 August 2019 / Published: 13 August 2019
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Abstract
We know a good deal about brain lateralization in birds and a good deal about animal welfare, but relatively little about whether there is a noteworthy relationship between avian welfare and brain lateralization. In birds, the left hemisphere is specialised to categorise stimuli [...] Read more.
We know a good deal about brain lateralization in birds and a good deal about animal welfare, but relatively little about whether there is a noteworthy relationship between avian welfare and brain lateralization. In birds, the left hemisphere is specialised to categorise stimuli and to discriminate preferred categories from distracting stimuli (e.g., food from an array of inedible objects), whereas the right hemisphere responds to small differences between stimuli, controls social behaviour, detects predators and controls attack, fear and escape responses. In this paper, we concentrate on visual lateralization and the effect of light exposure of the avian embryo on the development of lateralization, and we consider its role in the welfare of birds after hatching. Findings suggest that light-exposure during incubation has a general positive effect on post-hatching behaviour, likely because it facilitates control of behaviour by the left hemisphere, which can suppress fear and other distress behaviour controlled by the right hemisphere. In this context, particular attention needs to be paid to the influence of corticosterone, a stress hormone, on lateralization. Welfare of animals in captivity, as is well known, has two cornerstones: enrichment and reduction of stress. What is less well-known is the link between the influence of experience on brain lateralization and its consequent positive or negative outcomes on behaviour. We conclude that the welfare of birds may be diminished by failure to expose the developing embryos to light but we also recognise that more research on the association between lateralization and welfare is needed. Full article
(This article belongs to the Special Issue Brain Functional Lateralization in Animals)
Open AccessArticle
Class of Analytic Functions Defined by q-Integral Operator in a Symmetric Region
Symmetry 2019, 11(8), 1042; https://doi.org/10.3390/sym11081042
Received: 19 July 2019 / Revised: 8 August 2019 / Accepted: 9 August 2019 / Published: 13 August 2019
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Abstract
The aim of the present paper is to introduce a new class of analytic functions by using a q-integral operator in the conic region. It is worth mentioning that these regions are symmetric along the real axis. We find the coefficient estimates, [...] Read more.
The aim of the present paper is to introduce a new class of analytic functions by using a q-integral operator in the conic region. It is worth mentioning that these regions are symmetric along the real axis. We find the coefficient estimates, the Fekete–Szegö inequality, the sufficiency criteria, the distortion result, and the Hankel determinant problem for functions in this class. Furthermore, we study the inverse coefficient estimates for functions in this class. Full article
(This article belongs to the Special Issue Integral Transformations, Operational Calculus and Their Applications)
Open AccessFeature PaperArticle
Estimation of Natural Radionuclides and Rare Earth Elements Concentration of the Rocks of Abu Khuruq Ring Complex, Egypt
Symmetry 2019, 11(8), 1041; https://doi.org/10.3390/sym11081041
Received: 19 July 2019 / Revised: 8 August 2019 / Accepted: 8 August 2019 / Published: 13 August 2019
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Abstract
The naturally occurring radionuclides (radium-226, thorium-232, potassium-40 and radon-222) were investigated in the alkaline rocks of Abu Khuruq Ring, southern Eastern Desert, Egypt. A high-resolution germanium detector was used for the detection of 40K, 232Th, and 226Ra (Canberra, GR4020 model) [...] Read more.
The naturally occurring radionuclides (radium-226, thorium-232, potassium-40 and radon-222) were investigated in the alkaline rocks of Abu Khuruq Ring, southern Eastern Desert, Egypt. A high-resolution germanium detector was used for the detection of 40K, 232Th, and 226Ra (Canberra, GR4020 model) while 222Rn concentration was measured by the Alpha-Guard Saphymo GmbH system, model PQ 2000 (AG). Major and rare earth elements (REEs) were assessed using the inductively coupled plasma mass spectrometry and atomic emission spectrometry techniques. Positive correlations were observed between REEs, indicating symmetrical chemical properties and their overall presence in the parent material—also, a positive correlation was observed between effective radium content and radon concentrations pointing to the strong linear dependency between both contents in the studied rocks. The average values of activity concentration of 40K, 232Th, 226Ra, and 222Rn were less than the suggested level by a factor of 1.38%, 3.16%, 2.09%, and 1.16%, respectively. Significant variations were found among the radiological hazards parameters, e.g., the mean value of the annual effective dose (0.55 mSv y−1) was more than the global reference value (0.41 mSv y−1) by a factor of 1.34. The calculated average value of the gamma index was 0.90, and that of the alpha index was 0.37. Hex, Hin and Raeq showed fewer average values than the standard values of unity and 370 Bq kg−1, respectively. Full article
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Open AccessArticle
Analysis of Acoustic Emission Characteristics and Damage Constitutive Model of Coal-Rock Combined Body Based on Particle Flow Code
Symmetry 2019, 11(8), 1040; https://doi.org/10.3390/sym11081040
Received: 14 July 2019 / Revised: 29 July 2019 / Accepted: 7 August 2019 / Published: 13 August 2019
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Abstract
In this manuscript, the numerical coal-rock combined bodies with different height ratios of rock part to coal-rock combined body (HRRC) were established by particle flow code (PFC) firstly, and then the influence of different HRRC on mechanical properties and numerical acoustic emission (AE) [...] Read more.
In this manuscript, the numerical coal-rock combined bodies with different height ratios of rock part to coal-rock combined body (HRRC) were established by particle flow code (PFC) firstly, and then the influence of different HRRC on mechanical properties and numerical acoustic emission (AE) characteristics of coal-rock combined bodies were investigated. Finally, the damage constitutive model of the coal-rock combined body was discussed. The research results show that with the increase of the HRRC, the UCS and the elastic modulus (E) of the combined coal-rock bodies increased. The failure of coal-rock combined bodies is mainly focused on the coal body. The evolution law of AE hits of coal-rock combined bodies have three stages, named stable stage, rapid ascending stage, and rapid descending stage. The damage variable curves of coal-rock combined body have two stages, named slowly damage stage and sharply damage stage. The damage constitutive relation based on AE hits can well reflect the stress-strain relationships with a lower HRRC. However, for a higher HRRC, the damage constitutive equation is not accurately and the damage of the rock part in the coal-rock-combined body should be considered. Full article
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Open AccessArticle
Particle Creation and Thermal Aspects of Viscous Generalized Cosmic Chaplygin Gas
Symmetry 2019, 11(8), 1039; https://doi.org/10.3390/sym11081039
Received: 19 June 2019 / Revised: 8 July 2019 / Accepted: 19 July 2019 / Published: 12 August 2019
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Abstract
We investigate the particle creation, as well as the thermodynamics phenomenon of viscous generalized cosmic Chaplygin gas as a cosmic fluid by assuming the flat FRW universe. For this purpose, we extract various parameters such as the energy density (ρ), [...] Read more.
We investigate the particle creation, as well as the thermodynamics phenomenon of viscous generalized cosmic Chaplygin gas as a cosmic fluid by assuming the flat FRW universe. For this purpose, we extract various parameters such as the energy density ( ρ ) , Hubble parameter ( H ) , declaration parameter ( q ) , temperature ( T f ) , and particle number density ( n ) in the presence of three different models of the particle creation rate ( Γ ). We discuss the validity of the generalized second law of thermodynamics and thermal equilibrium condition under three models of Γ and discuss the graphical behavior of above-mentioned terms. Full article
(This article belongs to the Special Issue Viscous Cosmology)
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Open AccessArticle
Numerical Simulation and Mathematical Modeling of Electro-Osmotic Couette–Poiseuille Flow of MHD Power-Law Nanofluid with Entropy Generation
Symmetry 2019, 11(8), 1038; https://doi.org/10.3390/sym11081038
Received: 18 July 2019 / Revised: 6 August 2019 / Accepted: 8 August 2019 / Published: 12 August 2019
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Abstract
The basic motivation of this investigation is to develop an innovative mathematical model for electro-osmotic flow of Couette–Poiseuille nanofluids. The power-law model is treated as the base fluid suspended with nano-sized particles of aluminum oxide (Al2O3). The uniform speed [...] Read more.
The basic motivation of this investigation is to develop an innovative mathematical model for electro-osmotic flow of Couette–Poiseuille nanofluids. The power-law model is treated as the base fluid suspended with nano-sized particles of aluminum oxide (Al2O3). The uniform speed of the upper wall in the axial path generates flow, whereas the lower wall is kept fixed. An analytic solution for nonlinear flow dynamics is obtained. The ramifications of entropy generation, magnetic field, and a constant pressure gradient are appraised. Moreover, the physical features of most noteworthy substantial factors such as the electro-osmotic parameter, magnetic parameter, power law fluid parameter, skin friction, Nusselt number, Brinkman number, volume fraction, and concentration are adequately delineated through various graphs and tables. The convergence analysis of the obtained solutions has been discussed explicitly. Recurrence formulae in each case are also presented. Full article
(This article belongs to the Special Issue Aero/Hydrodynamics and Symmetry)
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Open AccessArticle
Necessary and Sufficient Optimality Conditions for Vector Equilibrium Problems on Hadamard Manifolds
Symmetry 2019, 11(8), 1037; https://doi.org/10.3390/sym11081037
Received: 18 July 2019 / Revised: 5 August 2019 / Accepted: 8 August 2019 / Published: 12 August 2019
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Abstract
The aim of this paper is to show the existence and attainability of Karush–Kuhn–Tucker optimality conditions for weakly efficient Pareto points for vector equilibrium problems with the addition of constraints in the novel context of Hadamard manifolds, as opposed to the classical examples [...] Read more.
The aim of this paper is to show the existence and attainability of Karush–Kuhn–Tucker optimality conditions for weakly efficient Pareto points for vector equilibrium problems with the addition of constraints in the novel context of Hadamard manifolds, as opposed to the classical examples of Banach, normed or Hausdorff spaces. More specifically, classical necessary and sufficient conditions for weakly efficient Pareto points to the constrained vector optimization problem are presented. The results described in this article generalize results obtained by Gong (2008) and Wei and Gong (2010) and Feng and Qiu (2014) from Hausdorff topological vector spaces, real normed spaces, and real Banach spaces to Hadamard manifolds, respectively. This is done using a notion of Riemannian symmetric spaces of a noncompact type as special Hadarmard manifolds. Full article
(This article belongs to the Special Issue Geometry of Submanifolds and Homogeneous Spaces)
Open AccessReview
Locality Sensitive Discriminative Unsupervised Dimensionality Reduction
Symmetry 2019, 11(8), 1036; https://doi.org/10.3390/sym11081036
Received: 15 July 2019 / Revised: 4 August 2019 / Accepted: 7 August 2019 / Published: 12 August 2019
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Abstract
Graph-based embedding methods receive much attention due to the use of graph and manifold information. However, conventional graph-based embedding methods may not always be effective if the data have high dimensions and have complex distributions. First, the similarity matrix only considers local distance [...] Read more.
Graph-based embedding methods receive much attention due to the use of graph and manifold information. However, conventional graph-based embedding methods may not always be effective if the data have high dimensions and have complex distributions. First, the similarity matrix only considers local distance measurement in the original space, which cannot reflect a wide variety of data structures. Second, separation of graph construction and dimensionality reduction leads to the similarity matrix not being fully relied on because the original data usually contain lots of noise samples and features. In this paper, we address these problems by constructing two adjacency graphs to stand for the original structure featuring similarity and diversity of the data, and then impose a rank constraint on the corresponding Laplacian matrix to build a novel adaptive graph learning method, namely locality sensitive discriminative unsupervised dimensionality reduction (LSDUDR). As a result, the learned graph shows a clear block diagonal structure so that the clustering structure of data can be preserved. Experimental results on synthetic datasets and real-world benchmark data sets demonstrate the effectiveness of our approach. Full article
(This article belongs to the Special Issue Selected Papers from IIKII 2019 conferences in Symmetry)
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Open AccessFeature PaperArticle
Revisiting a Negative Cosmological Constant from Low-Redshift Data
Symmetry 2019, 11(8), 1035; https://doi.org/10.3390/sym11081035
Received: 18 July 2019 / Revised: 6 August 2019 / Accepted: 8 August 2019 / Published: 10 August 2019
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Abstract
Persisting tensions between high-redshift and low-redshift cosmological observations suggest the dark energy sector of the Universe might be more complex than the positive cosmological constant of the ΛCDM model. Motivated by string theory, wherein symmetry considerations make consistent AdS backgrounds (i.e., maximally-symmetric [...] Read more.
Persisting tensions between high-redshift and low-redshift cosmological observations suggest the dark energy sector of the Universe might be more complex than the positive cosmological constant of the Λ CDM model. Motivated by string theory, wherein symmetry considerations make consistent AdS backgrounds (i.e., maximally-symmetric spacetimes with a negative cosmological constant) ubiquitous, we explore a scenario where the dark energy sector consists of two components: a negative cosmological constant, with a dark energy component with equation of state w ϕ on top. We test the consistency of the model against low-redshift baryon acoustic oscillation and Type Ia supernovae distance measurements, assessing two alternative choices of distance anchors: the sound horizon at baryon drag determined by the Planck collaboration and the Hubble constant determined by the SH0ES program. We find no evidence for a negative cosmological constant and mild indications for an effective phantom dark energy component on top. A model comparison analysis reveals that the Λ CDM model is favoured over our negative cosmological constant model. While our results are inconclusive, should low-redshift tensions persist with future data, it would be worth reconsidering and further refining our toy negative cosmological constant model by considering realistic string constructions. Full article
(This article belongs to the Special Issue Anomalies and Tensions of the Cosmic Microwave Background)
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