Symmetry2016, 8(9), 85; doi:10.3390/sym8090085 (registering DOI) - published 26 August 2016 Show/Hide Abstract
Abstract: Mobile communication security techniques are employed to guard the communication between the network entities. Mobile communication cellular systems have become one of the most important communication systems in recent times and are used by millions of people around the world. Since the 1990s, considerable efforts have been taken to improve both the communication and security features of the mobile communications systems. However, these improvements divide the mobile communications field into different generations according to the communication and security techniques such as A3, A5 and A8 algorithms for 2G-GSM cellular system, 3G-authentication and key agreement (AKA), evolved packet system-authentication and key agreement (EPS-AKA), and long term evolution-authentication and key agreement (LTE-AKA) algorithms for 3rd generation partnership project (3GPP) systems. Furthermore, these generations have many vulnerabilities, and huge security work is involved to solve such problems. Some of them are in the field of the public key cryptography (PKC) which requires a high computational cost and more network flexibility to be achieved. As such, the public key infrastructure (PKI) is more compatible with the modern generations due to the superior communications features. This paper surveys the latest proposed works on the security of GSM, CDMA, and LTE cellular systems using PKI. Firstly, we present the security issues for each generation of mobile communication systems, then we study and analyze the latest proposed schemes and give some comparisons. Finally, we introduce some new directions for the future scope. This paper classifies the mobile communication security schemes according to the techniques used for each cellular system and covers some of the PKI-based security techniques such as authentication, key agreement, and privacy preserving.
Symmetry2016, 8(9), 84; doi:10.3390/sym8090084 - published 25 August 2016 Show/Hide Abstract
Abstract: This article is devoted to the application of the cellular automata mathematical apparatus to the problem of continuous optimization. The cellular automaton with an objective function is introduced as a new modification of the classic cellular automaton. The algorithm of continuous optimization, which is based on dynamics of the cellular automaton having the property of geometric symmetry, is obtained. The results of the simulation experiments with the obtained algorithm on standard test functions are provided, and a comparison between the analogs is shown.
Symmetry2016, 8(9), 83; doi:10.3390/sym8090083 - published 24 August 2016 Show/Hide Abstract
Abstract: Optics has proved a fertile ground for the experimental simulation of quantum mechanics. Most recently, optical realizations of -symmetric quantum mechanics have been shown, both theoretically and experimentally, opening the door to international efforts aiming at the design of practical optical devices exploiting this symmetry. Here, we focus on the optical -symmetric dimer, a two-waveguide coupler where the materials show symmetric effective gain and loss, and provide a review of the linear and nonlinear optical realizations from a symmetry-based point of view. We go beyond a simple review of the literature and show that the dimer is just the smallest of a class of planar N-waveguide couplers that are the optical realization of the Lorentz group in 2 + 1 dimensions. Furthermore, we provide a formulation to describe light propagation through waveguide couplers described by non-Hermitian mode coupling matrices based on a non-Hermitian generalization of the Ehrenfest theorem.
Symmetry2016, 8(8), 81; doi:10.3390/sym8080081 - published 20 August 2016 Show/Hide Abstract
Abstract: The standard model involves particle symmetry and the mechanism of its breaking. Modern cosmology is based on inflationary models with baryosynthesis and dark matter/energy, which involves physics beyond the standard model. Studies of the physical basis of modern cosmology combine direct searches for new physics at accelerators with its indirect non-accelerator probes, in which cosmological consequences of particle models play an important role. The cosmological reflection of particle symmetry and the mechanisms of its breaking are the subject of the present review.
Symmetry2016, 8(8), 82; doi:10.3390/sym8080082 - published 20 August 2016 Show/Hide Abstract
Abstract: The Goldberg construction of symmetric cages involves pasting a patch cut out of a regular tiling onto the faces of a Platonic host polyhedron, resulting in a cage with the same symmetry as the host. For example, cutting equilateral triangular patches from a 6.6.6 tiling of hexagons and pasting them onto the full triangular faces of an icosahedron produces icosahedral fullerene cages. Here we show that pasting cutouts from a 6.6.6 tiling onto the full hexagonal and triangular faces of an Archimedean host polyhedron, the truncated tetrahedron, produces two series of tetrahedral (Td) fullerene cages. Cages in the first series have 28n2 vertices (n ≥ 1). Cages in the second (leapfrog) series have 3 × 28n2. We can transform all of the cages of the first series and the smallest cage of the second series into geometrically convex equilateral polyhedra. With tetrahedral (Td) symmetry, these new polyhedra constitute a new class of “convex equilateral polyhedra with polyhedral symmetry”. We also show that none of the other Archimedean polyhedra, six with octahedral symmetry and six with icosahedral, can host full-face cutouts from regular tilings to produce cages with the host’s polyhedral symmetry.
Symmetry2016, 8(8), 80; doi:10.3390/sym8080080 - published 17 August 2016 Show/Hide Abstract
Abstract: We have investigated Mn, Co and Ni substitution effects on polycrystalline samples of LaFePO0.95F0.05 by resistivity and magnetoresistance measurements. In LaFe1-xMxPO0.95F0.05 (M = Mn, Co and Ni), the superconducting transition temperature (Tc) monotonously decreases with increasing the impurity doping level of x. There is a clear difference of Tc suppression rates among Mn, Co and Ni doping cases, and the decreasing rate of Tc by Mn doping as a magnetic impurity is larger than those by the nonmagnetic doping impurities (Co/Ni). This result indicates that in LaFePO0.95F0.05, Tc is rapidly suppressed by the pair-breaking effect of magnetic impurities, and the pairing symmetry is a full-gapped s-wave. In the nonmagnetic impurity-doped systems, the residual resistivity in the normal state has nearly the same value when Tc becomes zero. The residual resistivity value is almost consistent with the universal value of sheet resistance for two-dimensional superconductors, suggesting that Tc is suppressed by electron localization in Co/Ni-doped LaFePO0.95F0.05.