| 1. |
- Montoya, Oscar Danilo, et al.
(författare)
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Optimal Demand Reconfiguration in Three-Phase Distribution Grids Using an MI-Convex Model
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:7
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Tidskriftsartikel (refereegranskat)abstract
- The problem of the optimal load redistribution in electrical three-phase medium-voltage grids is addressed in this research from the point of view of mixed-integer convex optimization. The mathematical formulation of the load redistribution problem is developed in terminals of the distribution node by accumulating all active and reactive power loads per phase. These loads are used to propose an objective function in terms of minimization of the average unbalanced (asymmetry) grade of the network with respect to the ideal mean consumption per-phase. The objective function is defined as the l1-norm which is a convex function. As the constraints consider the binary nature of the decision variable, each node is conformed by a 3×3 matrix where each row and column have to sum 1, and two equations associated with the load redistribution at each phase for each of the network nodes. Numerical results demonstrate the efficiency of the proposed mixed-integer convex model to equilibrate the power consumption per phase in regards with the ideal value in three different test feeders, which are composed of 4, 15, and 37 buses, respectively.
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| 2. |
- Abu-Youssef, Morsy A. M., et al.
(författare)
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Molecular, supramolecular structures combined with hirshfeld and dft studies of centrosymmetric m(Ii)-azido {m=ni(ii), fe(ii) or zn(ii)} complexes of 4-benzoylpyridine
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- The supramolecular structures of the three metal (II) azido complexes [Fe(4bzpy)4 (N3 )2 ]; 1, [Ni(4bzpy)4 (N3 )2 ]; 2 and [Zn(4bzpy)2 (N3 )2 ]n; 3 with 4-benzoylpyridine (4bzpy) were presented. All complexes contain hexa-coordinated divalent metal ions with a slightly distorted octahedral MN6 coordination sphere. Complexes 1 and 2 are monomeric with terminal azido groups while 3 is one-dimensional coordination polymer containing azido groups with µ(1,1) and µ(1,3) bridging modes of bonding. Hirshfeld analysis was used to quantitatively determine the different contacts affecting the molecular packing in the studied complexes. The most common interactions are the polar O … H and N … H interactions and the hydrophobic C … H contacts. The charges at the M(II) sites are calculated to be 1.004, 0.847, and 1.147 e for complexes 1–3, respectively. The degree of asymmetry is the highest in the case of the terminal azide in complexes 1 and 2 while was found the lowest in the µ(1,1) and µ(1,3) azide bonding modes in the Zn(II) complex 3. These facts were further explained in terms of atoms in molecules (AIM) topological parameters.
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| 3. |
- Ardonne, Eddy, et al.
(författare)
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Classification of Metaplectic Fusion Categories
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we study a family of fusion and modular systems realizing fusion categories Grothendieck equivalent to the representation category for so(2p+1)2. These categories describe non-abelian anyons dubbed ‘metaplectic anyons’. We obtain explicit expressions for all the F- and R-symbols. Based on these, we conjecture a classification for their monoidal equivalence classes from an analysis of their gauge invariants and define a function which gives us the number of classes.
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| 4. |
- Bashitialshaer, Raed, et al.
(författare)
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Obstacle Comparisons to Achieving Distance Learning and Applying Electronic Exams during COVID-19 Pandemic
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to identify obstacles and barriers to achieving quality distance learning and the use of electronic exams, comparing them to pursue success in the distance education system during the coronavirus pandemic (COVID-19). It also aimed to determine the similarity and differences between the two main components of distance education. This is based on a sample of evaluations from professors and students at universities in the Arab world, i.e., Algerian, Egyptian, Iraqi, and Palestinian universities. We used a descriptive approach using questionnaires (open question) with conveniently selected samples from two different groups: (1) 400 professors and student’s feedback from 600 distributed (i.e., Algerian, Egyptian, Palestinian, and Iraqi) and (2) 152 professors and student’s feedback from 300 distributed (i.e., Palestinian universities in the governorates of Gaza). The results indicated that professors and students faced 27 barriers in both distance learning and electronic exams, which are divided into four groups (categories) according to the sample. Recommendations to understand and overcome these obstacles will also be presented to improve distance learning and e-exams in the future. It is important to coordinate efforts in the development of distance education, especially concerning universities using distance learning and e-exams.
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| 5. |
- Berggren, Åsa, et al.
(författare)
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The Relationship Between Morphological Symmetry and Immune Response in Wild-Caught Adult Bush-Crickets
- 2009
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 1, s. 106-114
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Tidskriftsartikel (refereegranskat)abstract
- Despite interest in the relationship between fluctuating asymmetry (FA), immune response and ecological factors in insects, little data are available from wild populations. In this study we measured FA and immune response in 370 wild-caught male bush-crickets, Metrioptera roeseli, from 20 experimentally introduced populations in southern-central Sweden. Individuals with more-symmetric wings had a higher immune response as measured by the cellular encapsulation of a surgically-implanted nylon monofilament. However, we found no relationship between measures of FA in other organs (i.e. tibia and maxillary palp) and immune response, suggesting that this pattern may reflect differing selection pressures
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| 6. |
- Dahlberg, Oskar, et al.
(författare)
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Fully Metallic Flat Lens Based on Locally Twist-Symmetric Array of Complementary Split-Ring Resonators
- 2019
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Ingår i: Symmetry. - : MDPI. - 2073-8994. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we demonstrate how twist symmetries can be employed in the design of flat lenses. A lens design is proposed, consisting of 13 perforated metallic sheets separated by an air gap. The perforation in the metal is a two-dimensional array of complementary split-ring resonators. In this specific design, the twist symmetry is local, as it is only applied to the unit cell of the array. Moreover, the twist symmetry is an approximation, as it is only applied to part of the unit cell. First, we demonstrate that, by varying the order of twist symmetry, the phase delay experienced by a wave propagating through the array can be accurately controlled. Secondly, a lens is designed by tailoring the unit cells throughout the aperture of the lens in order to obtain the desired phase delay. Simulation and measurement results demonstrate that the lens successfully transforms a spherical wave emanating from the focal point into a plane wave at the opposite side of the lens. The demonstrated concepts find application in future wireless communication networks where fully-metallic directive antennas are desired.
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| 7. |
- Farooq, Muhammad, et al.
(författare)
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Computing Expectiles Using k-Nearest Neighbours Approach
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:4
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Tidskriftsartikel (refereegranskat)abstract
- Expectiles have gained considerable attention in recent years due to wide applications in many areas. In this study, the k-nearest neighbours approach, together with the asymmetric least squares loss function, called ex-kNN, is proposed for computing expectiles. Firstly, the effect of various distance measures on ex-kNN in terms of test error and computational time is evaluated. It is found that Canberra, Lorentzian, and Soergel distance measures lead to minimum test error, whereas Euclidean, Canberra, and Average of (L1,L∞) lead to a low computational cost. Secondly, the performance of ex-kNN is compared with existing packages er-boost and ex-svm for computing expectiles that are based on nine real life examples. Depending on the nature of data, the ex-kNN showed two to 10 times better performance than er-boost and comparable performance with ex-svm regarding test error. Computationally, the ex-kNN is found two to five times faster than ex-svm and much faster than er-boost, particularly, in the case of high dimensional data.
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| 8. |
- Ferrari, Arnaud, 1973-, et al.
(författare)
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Exploration of Extended Higgs Sectors with Run-2 Proton-Proton Collision Data at the LHC
- 2021
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Ingår i: Symmetry. - : MDPI. - 2073-8994. ; 13:11
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Tidskriftsartikel (refereegranskat)abstract
- One doublet of complex scalar fields is the minimal content of the Higgs sector in order to achieve spontaneous electroweak symmetry breaking and, in turn, to generate the masses of fundamental particles in the Standard Model. However, several theories beyond the Standard Model predict a nonminimal Higgs sector and introduce additional singlets, doublets or even higher-order weak isospin representations, thereby yielding additional Higgs bosons. With its high proton-proton collision energy (13 TeV during Run-2), the Large Hadron Collider opens a new window towards the exploration of extended Higgs sectors. This review article summarises the current state-of-the-art experimental results recently obtained in searches for new neutral and charged Higgs bosons with a partial or full Run-2 dataset.
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| 9. |
- Fisher, W.P., Jr.
(författare)
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Bateson and wright on number and quantity : How to not separate thinking from its relational context
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:8
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Tidskriftsartikel (refereegranskat)abstract
- As part of his explication of the epistemological error made in separating thinking from its ecological context, Bateson distinguished counts from measurements. With no reference to Bateson, the measurement theory and practice of Benjamin Wright also recognizes that number and quantity are different logical types. Describing the confusion of counts and measures as schizophrenic, like Bateson, Wright, a physicist and certified psychoanalyst, showed mathematically that convergent stochastic processes informing counts are predictable in ways that facilitate methodical measurements. Wright’s methods experimentally evaluate the complex symmetries of nonlinear and stochastic numeric patterns as a basis for estimating interval quantities. These methods also retain connections with locally situated concrete expressions, mediating the data display by contextualizing it in relation to the abstractly communicable and navigable quantitative unit and its uncertainty. Decades of successful use of Wright’s methods in research and practice are augmented in recent collaborations of metrology engineers and psychometricians who are systematically distinguishing numeric counts from measured quantities in new classes of knowledge infrastructure. Situating Wright’s work in the context of Bateson’s ideas may be useful for infrastructuring new political, economic, and scientific outcomes. © 2021 by the author.
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| 10. |
- Gudkov, Vladimir, et al.
(författare)
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A Possible Neutron-Antineutron Oscillation Experiment at PF1B at the Institut Laue Langevin
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- We consider a possible neutron–antineutron (n−n¯) oscillation experiment at the PF1B instrument at Institut Laue Langevin. It can improve the best existing constraint on the transition rate and also allow the testing of the methods and instrumentation which would be needed for a later larger-scale experiment at ESS. The main gain factors over the most competitive experiment, performed earlier at PF1 instrument at ILL, are: a more intense neutron beam and a new operating mode based on coherent n and n¯ mirror reflections. The installation of such an experiment would need a temporary replacement of the existing ballistic neutron guide by a specially designed n/n¯ guide with a gradually increasing cross section and a specially selected coating as well as the development and construction of an advanced n¯ annihilation detector with a high efficiency and low background. The overall gain factor could reach up to an order of magnitude and depends on the chosen experiment configuration.
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