#### Results in Journal Symmetry: 7,960

##### (searched for: journal_id:(777411))
Page of 160
Articles per Page
by
Show export options
Select all
Published: 27 January 2022
by MDPI
Abstract:
In this paper, under symmetric properties of multivalued operators, the existence of mild solutions as well as optimal control for the nonlocal problem of fractional semilinear evolution inclusions are investigated in abstract spaces. At first, the existence results are proved by applying the theory of operator semigroups and the fixed-point theorem of multivalued mapping. Then the existence theorem on the optimal state-control pair is proved by constructing the minimizing sequence twice. An example is given in the last section as an application of the obtained conclusions.
Published: 27 January 2022
by MDPI
Abstract:
Multidimensional potential energy surfaces for heavy noble gas–propylene oxide systems are obtained by applying the phenomenological method successfully used to describe homologous systems involving He and Ne atoms. Such potential energy surfaces, where the interaction exclusively arises from the anisotropic van der Waals interaction components, are given in an analytical form. Therefore, they can be easily used as force fields to carry out molecular simulations to evaluate spectroscopic features and the dynamical selectivity of weakly bound complexes formed by propylene oxide (a prototype chiral species) with a noble gas atom (a prototype isotropic partner) by two-body collisions under a variety of conditions. Several potential energy minima are identified on the surfaces, which are confirmed and characterized by high level ab initio calculations. The next step to further generalize this methodology is its extension to systems involving propylene oxide-diatomic molecules (as H2, O2 and N2), as well as to propylene oxide dimers.
Published: 27 January 2022
by MDPI
Abstract:
For collision-free navigation in unstructured and cluttered environments, deep reinforcement learning (DRL) has gained extensive successes for being capable of adapting to new environments without much human effort. However, due to its asymmetry, the problems related to its lack of data efficiency and robustness remain as challenges. In this paper, we present a new laser-based navigation system for mobile robots, which combines a global planner with reinforcement learning-based local trajectory re-planning. The proposed method uses Proximal Policy Optimization to learn an efficient and robust local planning policy with asynchronous data generation and training. Extensive experiments have been presented, showing that the proposed system achieves better performance than previous methods including end-to-end DRL, and it can improve the asymmetrical performance. Our analysis show that the proposed method can efficiently avoid deadlock points and achieves a higher success rate. Moreover, we show that our system can generalize to unseen environments and obstacles with only a few shots. The model enables the warehouse to realize automatic management through intelligent sorting and handling, and it is suitable for various customized application scenarios.
Published: 27 January 2022
by MDPI
Abstract:
To improve the accuracy of a symmetrical structural rolling bearing life prediction under noise interference, a multi-bearing life prediction method combining Ensemble Empirical Mode Decomposition (EEMD) and Bi-directional Long Short-Term Memory (BiLSTM) is proposed. First, EEMD is proposed to decompose the original vibration signal to obtain a finite number of Intrinsic Mode Function (IMF), and the IMFs are further filtered by combining the correlation criterion and kurtosis criterion. Then, the time domain features and frequency domain features of the reconstructed signal are filtered by monotonicity index to obtain the set of features containing key information. Finally, the BiLSTM network is trained on the filtered features set, and the method is proved to accurately predict the remaining life of rolling bearings under different operating conditions through rolling bearing full-life experiments, and the effectiveness of the method is verified by comparing the prediction results with several main recurrent neural networks.
Published: 27 January 2022
by MDPI
Abstract:
In order to raise the hysteresis loops in stationary dynamic regimes in the case of elastomeric insulators, specialized dynamic stands are used that may obtain both the necessary harmonic excitation by force as well as the modification of the angular arrangement discreetly variable from zero to 90 degrees. In this context, for the evaluation of the elastomeric insulators, a dynamic stand with an inertial vibrator was used, the frequency of which can be changed by continuous adjustment within the range of values from 2 Hz to 60 Hz. Forces and displacements can be measured with the appropriate sensors, and based on the recording of signals, the characteristics of rigidity, damping and the raise of hysteresis loops could be determined for three significant dynamic regimes: ante-resonance and post-resonance. Research on the dynamic stand, patented in Romania, has highlighted the fact that the parametric evaluation can be performed based on the lifting of the hysteretic loops in stationary harmonic regimes. Additionally, there are two situations specifically mentioned, one in which the significant inertial effect for the F-x loops leads to their positioning in quadrants II and IV, and the case of Q-x loops, where the inertial effect does not exist, and their positioning is only in quadrants I and III. From the analysis of the two cases, the most advantageous evaluation method for the test can be chosen. This article provides the calculation relationships established for the dynamic model with linear viscoelastic behaviour. The requirements of Voight–Kelvin modeling with a single degree of freedom is fully justified and ensured by the conditions of geometric and mass symmetry in the construction of the stand. The verification of the numerical results with the experimental ones was performed with the hysteresis loops corresponding to the previously defined three significant dynamic regimes, as well as according to the three positions of the elastomeric insulators for compression, compression-shear and shear.
Published: 27 January 2022
by MDPI
Abstract:
Considering the actual situation of moving vehicles acting on road surfaces, a dynamic model of a heavy vehicle–road coupling system was established based on the traditional vehicle–road vibration model. Firstly, a seven-degree-of-freedom vehicle model was established, and the vibration characteristics of the road subsystem were considered part of the whole system. The excitation effect of road roughness on the vehicle model was considered, and the dynamic model of the coupling system was finally obtained by combining the displacement compatibility principle of the contact relationship between the wheels and the road surface. The results show that the maximum bending value of the surface course reaches 2.37 mm. The maximum shear stress in the middle part of the surface course is 43,858 Pa. The vertical dynamic stress in the middle part of the surface course is larger, reaching 119,373 Pa, while the value of the vertical dynamic stress in the subgrade is much smaller, reaching 5824 Pa. The coupling dynamic model can reflect the relationship between the moving vehicle and the road and the dynamic performance, which not only provides theoretical support for the design parameters of heavy-duty vehicles but also provides a reference for the design of road durability.
Published: 27 January 2022
by MDPI
Abstract:
Radio telescopes are important for the development of society. With the advent of China’s Five-hundred-meter Aperture Spherical radio Telescope (FAST), adjusting the reflector panel to improve the reception ability is becoming an urgent problem. In this paper, an active control model of the reflector panel is established that considers the minimum sum of the radial offset of the actuator and the non-smoothness of the working paraboloid. Using the idea of discretization, the adjusted position of the main cable nodes, the ideal parabolic equation, and the expansion of each actuator are obtained by inputting the elevation and azimuth angle of the incident electromagnetic wave. To find the ideal parabola, a univariate optimization model is established, and the Fibonacci method is used to search for the optimal solution $h=-0.33018$ (offset in the direction away from the sphere’s center) and the focal diameter ratio $f=0.4671$ of the parabolic vertex. The ideal two-dimensional parabolic equation is then determined as ${x}^{2}-555.25z-166757.2=0$, and the ideal three-dimensional paraboloid equation is determined to be $z=\left({x}^{2}+{y}^{2}\right)/555.25-300.33018$. Moreover, the amount of the nodes and triangular reflection panels are calculated, which were determined to be 706 and 1325, respectively. The ratio reception of the working paraboloid and the datum sphere are $9.434%$ and $1.3898%$, respectively. The latter is calculated through a ray tracing simulation using the optical system modeling software LightTools.
Published: 27 January 2022
by MDPI
Abstract:
The efforts to reveal, in detail, the molecular and intramolecular structures of one of the main lipid classes, namely, triacyl-sn-glycerols, which are now known to affect their specific and important role in all living organisms, are briefly overviewed. Some milestones of significance in the gradual but continuous development and improvement of the analytical methodology to identify the triacylglycerol regio- and stereoisomers in complex lipid samples are traced throughout the years: the use of chromatography based on different separation principles; the improvements in the chromatographic technique; the development and use of different detection techniques; the attempts to simplify and automatize the analysis without losing the accuracy of identification. The spectacular recent achievements of two- and multidimensional methods used as tools in lipidomics are presented.
Published: 26 January 2022
by MDPI
Abstract:
To describe the distribution law of the degree of stratigraphic deformation in the cross-fault region under the influence of fault dislocation, the concept of deformation intensity is introduced, and a computational model of the coseismic deformation field in the cross-fault region is established based on the dislocation model theory and the rich fault inversion parameters in the Sichuan–Tibet region. According to the deformation law of a typical earthquake in Yushu, key sections and parameters are selected for analysis. The results show that the maximum dislocation of the deformation field in the cross-fault region decays from the fault rupture to the surface, and the deformation influence extends from the upper edge of the fault to the surface, with an overall funnel-shaped symmetric distribution. The deformation intensity is elliptically distributed in the vertical profile. The maximum deformation of the strata across the fault within the burial depth of the structure is fitted to fill the lack of the existing statistical equation of coseismic deformation without considering the burial depth factor. Finally, the strata are zoned by deformation intensity according to the degree of deformation to provide a reference for the seismic protection of structures in the near-fault area.
Published: 26 January 2022
by MDPI
Abstract:
We study the spectrality of a class of self-affine measures with prime determinant. Spectral measures are connected with fractal geometry that shows some kind of geometrical self-similarity under magnification. To make the self-affine measure becomes a spectral measure with lattice spectrum, we provide two new sufficient conditions related to the elements of digit set and zero set, respectively. The two sufficient conditions are more precise and easier to be verified as compared with the previous research. Moreover, these conditions offer a fresh perspective on a conjecture of Lagarias and Wang.
Published: 26 January 2022
by MDPI
Abstract:
The Fourier transform for slowly increasing functions is defined by the Parseval equation for tempered distributions. This definition was supplemented by a novel method of performing practical calculations by computing the Fourier transform for a suitably tempered function and then by integration by parts. The application of this method is illustrated both for the toy case, in which the function is integrable, so its Fourier transform can also be computed using the standard formula, and for the case of Coulomb-like potentials, which are only locally integrable functions. All of them have spherical symmetry, and two of them additionally have dilation symmetry. The proposed novel method does not violate these symmetries at any stage of the calculation.
Published: 26 January 2022
by MDPI
Abstract:
In the Internet of Things (IoT), many devices can communicate with each other directly through the Internet, and there are already good applications in transportation systems, smart meters, and smart home appliances. Wireless sensor networks are used in these Internet of things applications. Playing a vital role, the upload of data requires multiple layers of transmission to reach the cloud. In the industrial control field, many IoT devices upload data to the cloud for storage, but the upload process is easily tampered with, and centralized cloud services also have security concerns. In addition, in the local IoT perception layer among them, the security of sensor identity verification is also very important for message transmission. The main reason why the past blockchain technology could not be widely used in industrial control and other application fields is the cost considerations, because the procedures for running blockchain nodes and uploading transactions are too expensive. Therefore, this paper proposes an IoT architecture based on the IOTA Tangle network to solve the centralization problem of IoT storage in the cloud, and uses the method of MAM (Masked Authenticated Message) to trace the information of WSNs, while achieving data security and data preservation. In the edge devices of WSNs, because of the insufficient memory and computing performance of many devices, it is impossible to perform proof of work calculations. Therefore, this paper uses the logical key hierarchy-based method to manage the sensors, and applies symmetric and asymmetric encryption in blockchain. The identity verification of the device can be effectively achieved, and the operating cost can be effectively reduced.
Published: 26 January 2022
by MDPI
Abstract:
In order to improve the ability of airspace management, a multi-attribute decision-making tool based on q-rung orthopair probability hesitant fuzzy GRA-TOPSIS is proposed to solve the problem of airspace operation effectiveness evaluation; this is in view of the fact that there are few airspace operation effectiveness evaluation methods in general aviation airports. Firstly, taking general aviation airports as the research object, a complete airspace operation effectiveness evaluation system is newly established, its evaluation indicators are introduced, and its multi-attribute decision-making ideas are explained. Then, based on the q-rung orthopair probability hesitant fuzzy set, a new distance measure and information aggregation operator are defined, which can better deal with symmetry information. Secondly, we build a deviation maximization model to calculate the attribute weights of indicator elements in the decision-making process. Then, we combine the GRA method and TOPSIS method to rank the airspace operation effectiveness evaluation schemes. Finally, combined with calculation examples and comparative analysis, the reliability and rationality of the method proposed in this paper are verified, and the symmetry relationship between the evaluation results and the actual situation is better reflected. Experiments show that the method proposed in this paper can obtain more accurate airspace operation effectiveness evaluation results, and can provide reference for related research.
Published: 26 January 2022
by MDPI
Abstract:
There is a wealth of materials that are beam sensitive and only exist in nanometric crystals, because the growth of bigger crystals is either impossible or so complicated that it is not reasonable to spend enough time and resources to grow big crystals before knowing their potential for research or applications. This difficulty is encountered in minerals, zeolites, metal-organic frameworks or molecular crystals, including pharmaceuticals and biological crystals. In order to study these crystals a structure determination method for beam sensitive crystals of nanometric size is needed. The nanometric size makes them destined for electron diffraction, since electrons interact much more strongly with matter than X-rays or neutrons. In addition, for the same amount of beam damage, electron diffraction yields more information than X-rays. The recently developed low-dose electron diffraction tomography (LD-EDT) not only combines the advantages inherent in electron diffraction, but is also optimized for minimizing the electron dose used for the data collection. The data quality is high, allowing not only the solution of complex unknown structures, but also their refinement taking into account the dynamical diffraction effects. Here we present several examples of crystals solved and refined by this method. The range of the crystals presented includes two synthetic oxides, Sr5CuGe9O24 and (Na2/3Mn1/3)3Ge5O12, a natural mineral (bulachite), and a metal organic framework (Mn-formiate). The dynamical refinement can be successfully performed on data sets that needed less than 0.1 e2 for the entire data set.
Published: 26 January 2022
by MDPI
Abstract:
For solving the problem of modeling and visualization of scattered data that should preserve some constraints, we use a modified Shepard type operator that is required to fulfill some special conditions, highlighting the symmetry with other methods. We illustrate the properties of the obtained operators by some numerical examples.
Published: 26 January 2022
by MDPI
Abstract:
Clustered data arise frequently in many practical applications whenever units are repeatedly observed under a certain condition. One typical example for clustered data are animal experiments, where several animals share the same cage and should not be assumed to be completely independent. Standard methods for the analysis of such data are Linear Mixed Models and Generalized Estimating Equations—however, checking their assumptions is not easy, especially in scenarios with small sample sizes, highly skewed, count, and ordinal or binary data. In such situations, Wilcoxon–Mann–Whitney type effects are suitable alternatives to mean-based or other distributional approaches. Hence, no specific data distribution, symmetric or asymmetric, is required. Within this work, we will present different estimation techniques of such effects in clustered factorial designs and discuss quadratic- and multiple contrast type-testing procedures for hypotheses formulated in terms of Wilcoxon–Mann–Whitney effects. Additionally, the framework allows for the occurrence of missing data: estimation and testing hypotheses are based on all-available data instead of complete-cases. An extensive simulation study investigates the precision of the estimators and the behavior of the test procedures in terms of their type-I error control. One real world dataset exemplifies the applicability of the newly proposed procedures.
Published: 26 January 2022
by MDPI
Abstract:
The Fokas–Lenells equation and its multi-component coupled forms have attracted the attention of many mathematical physicists. The Fokas–Lenells equation and two coupled Fokas–Lenells equations are investigated from the perspective of Lie symmetries and conservation laws. The three systems have been turned into real multi-component coupled systems by appropriate transformations. By procedures of symmetry analysis, Lie symmetries of the three real systems are obtained. Explicit conservation laws are constructed using the symmetry/adjoint symmetry pair method, which depends on Lie symmetries and adjoint symmetries. The relationships between the multiplier and the adjoint symmetry are investigated.
Published: 25 January 2022
by MDPI
Abstract:
For over 100 y, scientists have investigated the properties of the proton, which is one of the most abundant components of visible matter in the universe. Nevertheless, researchers do not fully understand many details about its internal structure and dynamics. Time-like electromagnetic form factors are some of the observable quantities that can help us achieve a deeper understanding. In this review article, we present an overview of the current experimental status in this field, consisting of measurements of the time-like reactions ${e}^{+}{e}^{-}\to p\overline{p}$ and $p\overline{p}\to {e}^{+}{e}^{-}$ and future measurements of $p\overline{p}\to {\mu }^{+}{\mu }^{-}$. The focus is put on recent high-precision results of the reaction ${e}^{+}{e}^{-}\to p\overline{p}$ that have been obtained after analyzing 688.5 pb${}^{-1}$ of data taken at the BESIII experiment. They are compared to and put into perspective with results from previous measurements in this channel. We discuss the channels $p\overline{p}\to {e}^{+}{e}^{-}$ and $p\overline{p}\to {\mu }^{+}{\mu }^{-}$ in terms of the few existing, as well as future measurements, which the PANDA experiment will perform. Finally, we review several new theoretical models and phenomenological approaches inspired by the BESIII high-precision results and then discuss their implications for a deeper understanding of the proton’s structure and inner dynamics.
Published: 25 January 2022
by MDPI
Abstract:
The manufacture of parts by metal forming is a widespread technique in sectors such as oil and gas and automotives. It is therefore important to make a research effort to know the correct set of parameters that allow the manufacture of correct parts. This paper presents a process analysis by means of the finite element model. The use case presented in this paper is that of a 3-m diameter pipe component with a thickness of 22 mm. In this type of application, poor selection of process conditions can result in parts that are out of tolerance, both in dimensions and shape. A 3D finite element model is made, and the symmetry of the tube section generated in 2D is analysed. As a novelty, an analysis of the process correction as a function of the symmetrical deformation of the material in this case in the form of a pipe is carried out. The results show a correct fitting of the model and give guidelines for manufacturing.
Published: 25 January 2022
by MDPI
Abstract:
A fractional-order wave equation is established and solved for a space of three dimensions using spherical coordinates. An equivalent fluid model is used in which the acoustic wave propagates only in the fluid saturating the porous medium; this model is a special case of Biot’s theory obtained by the symmetry of the Lagrangian (invariance by translation and rotation). The basic solution of the wave equation is obtained in the time domain by analytically calculating Green’s function of the porous medium and using the properties of the Laplace transforms. Fractional derivatives are used to describe, in the time domain, the fluid–structure interactions, which are of the inertial, viscous, and thermal kind. The solution to the fractional-order wave equation represents the radiation field in the porous medium emitted by a point source. An important result obtained in this study is that the solution of the fractional equation is expressed by recurrence relations that are the consequence of the modified Bessel function of the third kind, which represents a physical solution of the wave equation. This theoretical work with analytical results opens up prospects for the resolution of forward and inverse problems allowing the characterization of a porous medium using spherical waves.
Published: 25 January 2022
by MDPI
Abstract:
Steganography is the technique for secretly hiding messages in media such as text, audio, image, and video without being discovered. Image is one of the most essential media for concealing data, making it hard to identify hidden data not visible to the human eye. In general, the cover image and the encrypted image are symmetrical in terms of dimension size, resolution, and qualities. This makes the difference difficult to perceive with the human eye. As a result, distinguishing between the two symmetric images required the development of methods. Steganalysis is a technique for identifying hidden messages embedded in digital material without having to know the embedding algorithm or the “non-stego” image. Due to their enormous feature vector dimension, which requires more time to calculate, the performance of most existing image steganalysis classification (ISC) techniques is still restricted. Therefore, in this research, we present a steganalysis classification method based on one of the texture features chosen, such as segmentation-based fractal texture analysis (SFTA), local binary pattern (LBP), and gray-level co-occurrence matrix (GLCM). The classifiers employed include Gaussian discriminant analysis (GDA) and naïve Bayes (NB). We used a public database in our proposed method and applied it to IStego100K datasets to be able to assess its performance. The experimental results reveal that in all classifiers, the SFTA feature surpassed all of the texture features, making it a great texture feature for image steganalysis classification. In terms of feature dimension and classification accuracy (CA), a comparison was made between the suggested SFTA-based GDA approach and various current ISC methods. The outcomes of the comparison are obvious show that the proposed method surpasses current methods.
Published: 25 January 2022
by MDPI
Abstract:
The possibility that a neutron can be transformed to a hidden sector particle remains intriguingly open. Proposed theoretical models conjecture that the hidden sector can be represented by a mirror sector, and the neutron n can oscillate into its sterile mirror twin ${n}^{\prime }$, exactly or nearly degenerate in mass with n. Oscillations $n-{n}^{\prime }$ can take place in vacuum or in an environment containing regular matter and a magnetic field, in which only the neutron will be subject to interactions with the environment. We describe the propagation of the oscillating $n-{n}^{\prime }$ system in a cold neutron beam passing through dense absorbing materials in connection to the possible regeneration type of experiments, where the effect of $n\to {n}^{\prime }\to n$ transformation can be observed.
Published: 25 January 2022
by MDPI
Abstract:
There is increasing interest in two-dimensional and quasi-two-dimensional materials and metamaterials for applications in chemistry, physics and engineering. Some of these applications are driven by the possible auxetic properties of such materials. Auxetic frameworks expand along one direction when subjected to a perpendicular stretching force. An equiauxetic framework has a unique mechanism of expansion (an equiauxetic mode) where the symmetry forces a Poisson’s ratio of $-1$. Hinged tilings offer opportunities for the design of auxetic and equiauxetic frameworks in 2D, and generic auxetic behaviour can often be detected using a symmetry extension of the scalar counting rule for mobility of periodic body-bar systems. Hinged frameworks based on Archimedean tilings of the plane are considered here. It is known that the regular hexagonal tiling, $\left\{{6}^{3}\right\}$, leads to an equiauxetic framework for both single-link and double-link connections between the tiles. For single-link connections, three Archimedean tilings considered as hinged body-bar frameworks are found here to be equiauxetic: these are $\left\{3.{12}^{2}\right\}$, $\left\{4.6.12\right\}$, and $\left\{4.{8}^{2}\right\}$. For double-link connections, three Archimedean tilings considered as hinged body-bar frameworks are found to be equiauxetic: these are $\left\{{3}^{4}\phantom{\rule{-0.166667em}{0ex}}.6\right\}$, $\left\{{3}^{2}\phantom{\rule{-0.166667em}{0ex}}.4.3.4\right\}$, and $\left\{3.6.3.6\right\}$.
Published: 25 January 2022
by MDPI
Abstract:
It is very important to evaluate the structural behavior of shield tunnel lining reasonably to ensure the safe operation and maintenance of subway trains. In this paper, by virtue of the resilience theory, the resilience evaluation of the existing shield tunnel lining induced by the symmetrical excavation of adjacent foundation pit is conducted using the numerical simulation. Firstly, the structural behavior index of the shield tunnel lining is defined. Moreover, using the evolution of structural behavior index along with the symmetrical excavation steps of adjacent foundation pit, the calculation method of the resilience index of the shield tunnel lining and grade of resilience are proposed. Secondly, numerical simulation is conducted to compare the degree of influence of three different block symmetrical excavation methods of the adjacent foundation pit on the structural deformation of existing shield tunnel lining. Finally, based on the proposed resilience evaluation method, the structural deformation index and the resilience index of the existing shield tunnel lining are calculated under three different block symmetrical excavation methods, which indicates that the control effect of different block symmetrical excavation methods of the adjacent foundation pit varies greatly. Moreover, it is necessary to adopt the fine excavation method of foundation pit by sections to better control the deformation of the existing shield tunnel lining.
Published: 25 January 2022
by MDPI
Abstract:
Computed tomography (CT) is the first modern slice-imaging modality. Recent years have witnessed its widespread application and improvement in detecting and diagnosing related lesions. Nonetheless, there are several difficulties in detecting lesions in CT images: (1) image quality degrades as the radiation dose is reduced to decrease radiational injury to the human body; (2) image quality is frequently hampered by noise interference; (3) because of the complicated circumstances of diseased tissue, lesion pictures typically show complex shapes; (4) the difference between the orientated object and the background is not discernible. This paper proposes a symmetry GAN detection network based on a one-stage detection network to tackle the challenges mentioned above. This paper employs the DeepLesion dataset, containing 10,594 CT scans (studies) of 4427 unique patients. The symmetry GANs proposed in this research consist of two distinct GAN models that serve different functions. A generative model is introduced ahead of the backbone to increase the input CT image series to address the typical problem of small sample size in medical datasets. Afterward, GAN models are added to the attention extraction module to generate attention masks. Furthermore, experimental data indicate that this strategy has significantly improved the model’s robustness. Eventually, the proposed method reaches 0.9720, 0.9858, and 0.9833 on P, R, and $mAP$, on the validation set. The experimental outcome shows that the suggested model outperforms other comparison models. In addition to this innovation, we are inspired by the innovation of the ResNet model in terms of network depth. Thus, we propose parallel multi-activation functions, an optimization method in the network width. It is theoretically proven that by adding coefficients to each base activation function and performing a softmax function on all coefficients, parallel multi-activation functions can express a single activation function, which is a unique ability compared to others. Ultimately, our model outperforms all comparison models in terms of P, R, and $mAP$, achieving 0.9737, 0.9845, and 0.9841. In addition, we encapsulate the model and build a related iOS application to make the model more applicable. The suggested model also won the second prize in the 2021 Chinese Collegiate Computing Competition.
Published: 25 January 2022
by MDPI
Abstract:
Traffic congestion is a global problem. Affected by climate, the issue of congestion in cold-climate cities is more serious. To comprehensively and accurately identify the traffic congestion situation on the main roads of cold-climate cities and to provide a reference for city managers for congestion treatment, this study applies the theory of potential energy to the problem of traffic congestion, draws on the symmetry of potential energy and the function mechanism of artificial potential fields, and establishes a traffic congestion potential energy model for the main roads in cold-climate cities. Taking Global Positioning System (GPS) data as the primary data, the model parameters are calibrated using a combination of subjective and objective empowerment methods, and the investigation into the congestion perception level determines the division threshold of the congestion potential energy level. Test results are encouraging, and the method considers the state and the trends and can avoid problems such as lagging road condition information.
Published: 25 January 2022
by MDPI
Abstract:
Finding reliable partners is the key to supply chain management. However, the symmetrical evaluation of enterprise trust is complex, so the decision-makers must understand its quantitative and qualitative characteristics in order to realize a reasonable evaluation. Based on the analysis of the causes and influencing factors of supply chain trust, this paper constructed four primary indexes and 16 secondary indexes to define enterprise trust, and used analytic network process (ANP) to evaluate and rank the indicators. Then, the paper constructed a supply chain directed weighted trust evolution network model based on complex network theory, integrated trust into the network with edge weights, and put forward the merit index of comprehensive node degree, weight, and efficiency to study the supply chain network evolution. The simulation results show that the node degree distribution in the trust evolution network conforms to the power-law distribution rule, and the trust evolution model of the complex network has obvious scale-free characteristics, which effectively avoid the situation that the node influence is too high due to the excessive strength of a single index. At the same time, it can quickly evaluate the node influence of the directed weighted complex network, and provide certain practical value for the node trust prediction of the supply chain network.
Published: 24 January 2022
by MDPI
Abstract:
Establishing a symmetrical model of surrounding vehicles and accurately obtaining the driving state of the surrounding vehicles in the driving environment can improve the safety of driving, which is an important issue that needs to be considered in the automatic driving system or auxiliary driving system. Therefore, we propose an adaptive unscented Kalman filter algorithm based on Interacting Multiple Model (IMM) theory to estimate the state of target vehicle in the high-speed driving environment. To be specific, we use the Constant Turn Rate and Acceleration (CTRA) theory to establish the target vehicle kinematics model, simultaneously, in order to overcome the problem of estimator failure when the yaw rate is close to zero, a simplified version of the CTRA model is also introduced into the estimation process. In addition, the parameter adaptation strategy is added, so the proposed estimator can overcome the uncertainty of the noise model and improve its accuracy. Finally, the effectiveness of proposed state estimation algorithm is verified on the Carsim and Simulink co-simulation platform. The results of simulations and experiments show that the accuracy and stability of IMM-based algorithm is better than the single-model algorithm in different scenarios, and the parameter adaptation strategy brings performance improvement.
Published: 24 January 2022
by MDPI
Abstract:
The molecular net complexity (HmolNet) is an extension of the combinatorial complexity (Hmol) of a crystal structure introduced by Krivovichev. It was calculated for a set of 4152 molecular crystal structures with the composition of CxHyOz characterized by the structural class P21/c, Z = 4 (1). The molecular nets were derived from the molecular Voronoi–Dirichlet Polyhedra (VDPmol). The values of the molecular coordination number (CNmol) and critical coordination number (CNcrit) are discussed in relation with the complexity of the crystal structures. A statistical distribution of the set of molecular crystals based on the values of CNmol, CNcrit, and the complexity parameters is obtained. More than a half of the considered structures has CNmol = 14 and CNmol′ = 9 with the Wyckoff set of edges e5dcba. The average multiplicity of intermolecular contacts statistically significantly decreases from 1.58 to 1.51 upon excluding all contacts except those bearing the molecular net. The normalized value of HmolNet is of the logistic distribution type and is distributed near 0.85HmolNet with a small standard deviation. The contribution of Hmol into HmolNet ranges from 35 to 95% (mean 79%, SD 6%), and the subset of bearing intermolecular contacts accounts for 41 to 100% (mean 62%, SD 11%) of the complexity of the full set of intermolecular contacts.
Published: 24 January 2022
by MDPI
Abstract:
Nonlinear dynamical models with parameters are at the heart of natural science, and they serve as essential instrument to analyze and solve various appealing problems in engineering areas
Published: 24 January 2022
by MDPI
Abstract:
This paper employs Lie symmetry analysis to recover cubic–quartic optical soliton solutions to the Lakshmanan–Porsezian–Daniel model in birefringent fibers. The results are a sequel to the previously reported work on the same model in unpolarized fibers. Dark, singular, and straddled optical solitons that emerged from the scheme are presented.
Published: 24 January 2022
by MDPI
Abstract:
To investigate the bearing behavior of symmetrical full-scale different strength concrete filled double skin steel tube (CFDST) stub columns, 19 full-scale specimens were designed, considering the slenderness ratio (λ); the compression strength of core concrete and sandwich concrete (fcki, fcko), the thickness of the inner and outer steel tubes (ti, to); the diameter of inner and outer steel tubes (Di, Do); and the tensile strength of the inner and outer steel tubes (fyki, fyko) as the main parameters. Nonlinear constitutive models for concrete considering constraint effect were adopted, and a finite element (FE) model was established using ABAQUS software. By comparing the results between simulations and experiments, the rationality of the modeling method was verified. Based on the FE model, the parameter analysis for CFDST columns were conducted, and the force mechanism, stress distribution, and deformation process were analyzed. The results showed that the axial compression bearing capacity (${N}_{\mathrm{s}}^{\mathrm{u}}$) increased significantly with an increase in fcki, to, Do, and fcko, while ${N}_{\mathrm{s}}^{\mathrm{u}}$ decreased gradually with an increase in λ. Finally, according to the calculated results of the specimens, the calculation formula for ${N}_{\mathrm{s}}^{\mathrm{u}}$ of full-scale composite columns was statistically regressed using 1stOpt software and showed a good agreement with the FE.
Published: 24 January 2022
by MDPI
Abstract:
To develop low-carbon transport and promote sustainable economic development, this paper took the uncertainty in highway transport speed and transshipment time into account in the actual transport process and established multi-objective path-decision models of multimodal transport under different carbon policies. The expectation values of nonlinear uncertainties were estimated by Law of Large Numbers (LLN), and the models were solved by the K-shortest paths algorithm and non-dominated sorting algorithm (NSGA-II), whose advancement and effectiveness were verified through the comparison of SPEA2. Based on the Pareto theory, the optimally symmetrical compromise between the objectives and the influence of the transport speed uncertainty and carbon emission policies on path decisions were quantified and discussed. Taking the multimodal transport network of West Africa as the experimental background, the practicability of the path-decision results is analyzed, and a trade-off analysis is also conducted to provide the theoretical foundation for future freight transport planning.
Published: 24 January 2022
by MDPI
Abstract:
The present work is connected to the study of electrode conditioning issues for the chemically modified electrodes (CMEs) prepared based on 2,6-bis((E)-2-(thiophen-2-yl)vinyl)-4-(5-isopropyl- 3,8-dimethylazulen-1-yl) pyridine (L). L is irreversibly electrooxidized to polymers leading to L-CMEs. The recognition experiments are the final test of chosen parameters (electropolymerization potential and charge in controlled potential electrolysis (CPE), anodic limit of the overoxidation cycles (OC), number of OC, anodic limit of the equilibration cycles (EC), number of EC, pH of the buffer solutions for HMs accumulation, complexation time, potential and time of reduction). The evidence of film deposition resulted by the change of ferrocene symmetrical signal characteristics on bare electrode in ferrocene solution was the simplest way to prove the formation of L-CMEs. However, finding the best electrode equilibration conditions turned out to be a source of increasing the analytical performance for the CMEs, especially those dedicated to the detection of Pb. The paper underlines the importance of understanding the role of each varied parameter, and of carrying out a systematic study of each possible variable. Optimum conditions for Pb ions analysis, using this new thiophen-vinyl-pyridine-azulene based CMEs, have been established, in order to get the best conditions for its detection in water.
Published: 24 January 2022
by MDPI
Abstract:
The modified Stokes second problem for incompressible upper-convected Maxwell (UCM) fluids with linear dependence of viscosity on the pressure is analytically and numerically investigated. The fluid motion, between infinite horizontal parallel plates, is generated by the lower wall, which oscillates in its plane. The movement region of the fluid is symmetric with respect to the median plane, but its motion is asymmetric due to the boundary conditions. Closed-form expressions are found for the steady-state components of start-up solutions for non-dimensional velocity and the corresponding non-trivial shear and normal stresses. Similar solutions for the simple Couette flow are obtained as limiting cases of the solutions corresponding to the motion due to cosine oscillations of the wall. For validation, it is graphically proved that the start-up solutions (numerical solutions) converge to their steady-state components. Solutions for motions of ordinary incompressible UCM fluids performing the same motions are obtained as special cases of present results using asymptotic approximations of standard Bessel functions. The time needed to reach the permanent or steady state is also determined. This time is higher for motions of ordinary fluids, compared with motions of liquids with pressure-dependent viscosity. The impact of physical parameters on the fluid motion and the spatial–temporal distribution of start-up solutions are graphically investigated and discussed. Ordinary fluids move slower than fluids with pressure-dependent viscosity.
Published: 23 January 2022
by MDPI
Abstract:
In this paper, the problem of vertical shear flow instabilities at the base of a river plume and their consequences in terms of turbulent energy production and mixing is addressed. This study was carried out using 2D non-hydrostatic simulations and a linear stability analysis. The initial conditions used in these simulations were similar to those observed in river plumes near estuaries. Unstable stratified sheared flows follow three stages of evolution: (i) the generation of billows induced by vertical shear instabilities, (ii) intensification, and (iii) elongation. The elongation of the generated billows is related to the strain intensity, which depends on the physical setting involved (velocity shear, stratification thickness, and bottom slope). Two vertical shear instabilities were found in our study: the Holmboe and Kelvin–Helmholtz instabilities. The Kelvin–Helmholtz instability has a smaller growth time and longer wavelengths; the Holmboe instability is characterized by a longer growth time and shorter wavelengths. The Kelvin–Helmholtz instability is intensified when the bottom is sloped and for large shears. The Holmboe instability is stronger when the stratification thickness is reduced compared to the shear thickness and when the bottom is sloped. For mixing, the flow can be: (i) pre-turbulent, (ii) quasi-turbulent, or (iii) turbulent. The pre-turbulent flow corresponds to more mass mixing than momentum mixing and to more Eddy Kinetic Energy dissipation than Eddy Available Potential Energy dissipation. Such a flow is encountered over a flat bottom whatever the initial shear is. The quasi-turbulent and turbulent flows are reached when the bottom is sloped and when the stratification thickness is reduced. Using turbulent mixing statistics (mixing coefficients, mixing efficiency, Eddy Kinetic Energy, and Eddy Available Potential Energy dissipation rates), we showed that, despite their slow growth, Holmboe instabilities contribute more efficiently to turbulent mixing than Kelvin–Helmholtz instabilities. Holmboe instabilities are the only source of turbulent mixing when sharp density gradients are observed (small buoyancy thickness experiment). Our simulations highlight the contribution of the Holmboe instability to turbulent mixing.
Published: 23 January 2022
by MDPI
Abstract:
Background: The recent experimental discovery of drip-line nucleus 39Na has attracted great interest in theoretical studies of exotic nuclear structures in this mass region. Methods: We solve the Skyrme–Hartree–Fock–Bogoliubov (Skyrme-HFB) equation within deformed coordinate-spaces. The present approach is suitable for descriptions of weakly bound deformed nuclei with continuum effects and deformed halo structures. Results: The systematical two-neutron separation energies are obtained with the SkM${}_{\mathrm{ext}1}^{*}$ and UNEDF0${}_{\mathrm{ext}1}$ forces for Na and Mg isotopes close to the neutron drip line. The density distributions show that ${}^{39}$Na and ${}^{42}$Mg have deformed halo structures. Furthermore, there are significant influences of various pairing interactions on halo shapes at large distances. Conclusions: Both ${}^{39}$Na and ${}^{42}$Mg are very weakly bound with well prolate deformed cores. However, their surface halo structures are dependent on the choices of pairing interactions. The volume-type pairing interaction tends to predict a prolate deformed halo, while the halo deformations at large distances are reduced by adopting the surface pairing. We demonstrate that ${}^{39}$Na and ${}^{42}$Mg are promising candidates for two-neutron deformed halo nuclei.
Published: 23 January 2022
by MDPI
Abstract:
In recent years, artificial intelligence techniques have become fundamental parts of various engineering research activities and practical realizations. The advantages of the neural networks, as one of the main artificial intelligence methods, make them very appropriate for different engineering design problems. However, the qualitative properties of the neural networks’ states are extremely important for their design and practical performance. In addition, the variety of neural network models requires the formulation of appropriate qualitative criteria. This paper studies a class of discrete Bidirectional Associative Memory (BAM) neural networks of the Cohen–Grossberg type that can be applied in engineering design. Due to the nature of the proposed models, they are very suitable for symmetry-related problems. The notion of the practical stability of the states with respect to sets is introduced. The practical stability analysis is conducted by the method of the Lyapunov functions. Examples are presented to verify the proposed criteria and demonstrate the efficiency of the results. Since engineering design is a constrained processes, the obtained stability of the sets’ results can be applied to numerous engineering design tasks of diverse interest.
Published: 23 January 2022
by MDPI
Abstract:
Encryption is the de facto method for protecting information, whether this information is locally stored or on transit. Although we have many encryption techniques, they have problems inherited from the computational models that they use. For instance, the standard encryption technique suffers from the substitution box syndrome—the substitution box does not provide enough confusion. This paper proffers a novel encryption method that is both highly secure and lightweight. The proposed technique performs an initial preprocessing on its input plaintext, using fuzzy substitutions and noising techniques to eliminate relationships to the input plaintext. The initially encrypted plaintext is next concealed in enormously complicated codes that are generated using a chaotic system, whose behavior is controlled by a set of operations and a nature-inspired triggering technique. The effectiveness of the security of the proposed technique is analyzed using rigorous randomness tests and entropy.
Published: 22 January 2022
by MDPI
Abstract:
Industrial network systems are facing various new challenges, such as increasing functional failure factors, the accelerating penetration of information threats, and complex and diverse attack methods. Industrial networks are often vulnerable to natural or intentional disasters; therefore, it is highly invaluable to research to identify the influential nodes. Most of the state-of-the-art evaluates the importance of the nodes according to one or more network metrics. Moreover, there are no metrics reflecting all the properties of the network. In this paper, a novel method (Structure-based Identification Method, SIM) to identify the influential nodes in industrial networks is proposed based on the network structure, which goes beyond the use of network metrics. The SIM method extracts the weakly connected components, which are more likely to survive after the important nodes are attacked in the network. Evaluation results show that the SIM method obtains better results than the state-of-the-art methods to identify influential nodes in real-world industrial networks and has a good prospect to be applied in industrial application.
Published: 22 January 2022
by MDPI
Abstract:
Paraoxonase 2 (PON2) is a member of a small family of human lactonases. Recently, post-translational modifications (PTMs) of PON2 were highlighted, one of which involved the modulation of the enzyme activity. Furthermore, two important single nucleotide polymorphisms (SNPs) involved in type 2 diabetes and its consequences, were found to modulate the enzyme activity as well. The position on the PON2 structural model of both residues corresponding to SNPs and PTMs suggested a symmetry of the molecule. By sequence and structure superposition we were able to confirm this finding. The result will be discussed in light of the evolution of symmetry in biological molecules and their function.
Published: 22 January 2022
by MDPI
Abstract:
We review and compare three algebraic methods to compute the nonlinearity of Boolean functions. Two of them are based on Gröbner basis techniques: the first one is defined over the binary field, while the second one over the rationals. The third method improves the second one by avoiding the Gröbner basis computation. We also estimate the complexity of the algorithms, and, in particular, we show that the third method reaches an asymptotic worst-case complexity of $O\left(n{2}^{n}\right)$ operations over the integers, that is, sums and doublings. This way, with a different approach, the same asymptotic complexity of established algorithms, such as those based on the fast Walsh transform, is reached.
Published: 22 January 2022
by MDPI
Abstract:
For a fixed pair of input and output states in the space ${H}_{A}$ of a system A, a quantum channel, i.e., a linear, completely positive and trace-preserving map, between them is not unique, in general. Here, this point is discussed specifically for a decoherence channel, which maps from a pure input state to a completely decoherent state like the thermal state. In particular, decoherence channels of two different types are analyzed: one is unital and the other is not, and both of them can be constructed through reduction of B in the total extended space ${H}_{A}\otimes {H}_{B}$, where ${H}_{B}$ is the space of an ancillary system B that is a replica of A. The nonuniqueness is seen to have its origin in the unitary symmetry in the extended space. It is shown in an example of a two-qubit system how such symmetry is broken in the objective subspace ${H}_{A}$ due to entanglement between A and B. A comment is made on possible relevance of the present work to nanothermodynamics in view of quantum Darwinism.
Published: 21 January 2022
by MDPI
Abstract:
We propose a motion planning method for automated vehicles (AVs) to complete driving tasks in dynamic traffic scenes. The proposed method aims to generate motion trajectories for an AV after obtaining the surrounding dynamic information and making a preliminary driving decision. The method generates a reference line by interpolating the original waypoints and generates optional trajectories with costs in a prediction interval containing three dimensions (lateral distance, time, and velocity) in the Frenet frame, and filters the optimal trajectory by a series of threshold checks. When calculating the feasibility of optional trajectories, the cost of all optional trajectories after removing obstacle interference shows obvious axisymmetric regularity concerning the reference line. Based on this regularity, we apply the constrained Simulated Annealing Algorithm (SAA) to improve the process of searching for the optimal trajectories. Experiments in three different simulated driving scenarios (speed maintaining, lane changing, and car following) show that the proposed method can efficiently generate safe and comfortable motion trajectories for AVs in dynamic environments. Compared with the method of traversing sampling points in discrete space, the improved motion planning method saves 70.23% of the computation time, and overcomes the limitation of the spatial sampling interval.
Published: 21 January 2022
by MDPI
Abstract:
The purpose of this research is to analyze the general equations of double diffusive magneto-free convection in an Oldroyd-B fluid flow based on the fundamental symmetry that are presented in non-dimensional form and are applied to a moving heated vertical plate as the boundary layer flow up, with the existence of an external magnetic field that is either moving or fixed consistent with the plate. The thermal transport phenomenon in the presence of constant concentration, coupled with a first order chemical reaction under the exponential heating of the symmetry of fluid flow, is analyzed. The Laplace transform method is applied symmetrically to tackle the non-dimensional partial differential equations for velocity, mass and energy. The contribution of mass, thermal and mechanical components on the dynamics of fluid are presented and discussed independently. An interesting property regarding the behavior of the fluid velocity is found when the movement is observed in the magnetic intensity along with the plate. In that situation, the fluid velocity is not zero when it is far and away from the plate. Moreover, the heat transfer aspects, flow dynamics and their credence on the parameters are drawn out by graphical illustrations. Furthermore, some special cases for the movement of the plate are also studied.
Published: 21 January 2022
by MDPI
Abstract:
A four-dimensional integral containing $g\left(x,y,z,t\right){C}_{n}^{\left(\lambda \right)}\left(x\right)$ is derived. ${C}_{n}^{\left(\lambda \right)}\left(x\right)$ is the Gegenbauer polynomial, $g\left(x,y,z,t\right)$ is a product of the generalized logarithm quotient functions and the integral is taken over the region $0\le x\le 1,0\le y\le 1,0\le z\le 1,0\le t\le 1$. The integral is difficult to compute in general. Special cases are given and invariant index forms are derived. The zero distribution of almost all Hurwitz–Lerch zeta functions is asymmetrical. All the results in this work are new.
Published: 21 January 2022
by MDPI
Abstract:
In this paper, the distributed unrelated parallel machines scheduling problem (DUPMSP) is studied and a hybrid imperialist competitive algorithm (HICA) is proposed to minimize total tardiness. All empires were categorized into three types: the strongest empire, the weakest empire, and other empires; the diversified assimilation was implemented by using different search operator in the different types of empires, and a novel imperialist competition was implemented among all empires except the strongest one. The knowledge-based local search was embedded. Extensive experiments were conducted to compare the HICA with other algorithms from the literature. The computational results demonstrated that new strategies were effective and the HICA is a promising approach to solving the DUPMSP.
Published: 21 January 2022
by MDPI
Abstract:
High-order Markov chains are very useful for the analysis of complex temporal relationships, but they generally require a very high number of parameters
Published: 21 January 2022
by MDPI
Abstract:
In this work, we propose, through the use of population-based metaheuristics, an optimization method that solves the problem of autonomous path tracking using a rear-wheel fuzzy logic controller. This approach enables the design of controllers using rules that are linguistically familiar to human users. Moreover, a new technique that uses three different paths to validate the performance of each candidate configuration is presented. We extend on our previous work by adding two more membership functions to the previous fuzzy model, intending to have a finer-grained adjustment. We tuned the controller using several well-known metaheuristic methods, Genetic Algorithms (GA), Particle Swarm Optimization (PSO), Grey Wolf Optimizer (GWO), Harmony Search (HS), and the recent Aquila Optimizer (AO) and Arithmetic Optimization Algorithms. Experiments validate that, compared to published results, the proposed fuzzy controllers have better RMSE-measured performance. Nevertheless, experiments also highlight problems with the common practice of evaluating the performance of fuzzy controllers with a single problem case and performance metric, resulting in controllers that tend to be overtrained.
Published: 21 January 2022
by MDPI
Abstract:
This research paper is dedicated to an investigation of an evolution problem under a new operator ($\mathfrak{g}$-Atangana–Baleanu–Caputo type fractional derivative)(for short, $\mathfrak{g}$-ABC). For the proposed problem, we construct sufficient conditions for some properties of the solution like existence, uniqueness and stability analysis. Existence and uniqueness results are proved based on some fixed point theorems such that Banach and Krasnoselskii. Furthermore, through mathematical analysis techniques, we analyze different types of stability results. The symmetric properties aid in identifying the best strategy for getting the correct solution of fractional differential equations. An illustrative example is discussed for the control problem.
Page of 160
Articles per Page
by
Show export options
Select all