| 1. |
- Antoniouk, Alexandra, V, et al.
(författare)
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A stochastic p-adic model of the capillary flow in porous random medium
- 2018
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Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 505, s. 763-777
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Tidskriftsartikel (refereegranskat)abstract
- We develop the p-adic model of propagation of fluids (e.g., oil or water) in capillary networks in a porous random medium. The hierarchic structure of a system of capillaries is mathematically modeled by endowing trees of capillaries with the structure of an ultra metric space. Considerations are restricted to the case of idealized networks represented by homogeneous p-trees with p branches leaving each vertex, where p > 1 is a prime number. Such trees are realized as the fields of p-adic numbers. We introduce and study an inhomogeneous Markov process describing the penetration of fluid into a porous random medium. (C) 2018 Elsevier B.V. All rights reserved.
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| 2. |
- Bech, Morten L, et al.
(författare)
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Mapping change in the overnight money market
- 2015
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Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 424, s. 44-51
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Tidskriftsartikel (refereegranskat)abstract
- We use an information-theoretic approach to describe changes in lending relationships between financial institutions around the time of the Lehman Brothers failure. Unlike previous work that conducts maximum likelihood estimation on undirected networks our analysis distinguishes between borrowers and lenders and looks for broader lending relationships (multi-bank lending cycles) that extend beyond the immediate counter-parties. We detect significant changes in lending patterns following implementation of the Interest on Required and Excess Reserves policy by the Federal Reserve in October 2008. Analysis of micro-scale rates of change in the data suggests these changes were triggered by the collapse of Lehman Brothers a few weeks before.
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| 3. |
- Benhouria, Y., et al.
(författare)
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Hysteresis loops and dielectric properties of a mixed spin Blume-Capel Ising ferroelectric nanowire
- 2018
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Ingår i: Physica A. - : ELSEVIER SCIENCE BV. - 0378-4371 .- 1873-2119. ; 506, s. 499-506
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Tidskriftsartikel (refereegranskat)abstract
- The critical and hysteresis behaviors of a ferrielectric Blume-Capel nanowire are studied using the 'sing model with mixed spins -(1/2,1) in the presence of both an external longitudinal electric (E-z) and crystal anisotropy (D) fields. We use the Monte Carlo simulations (MCs) to examine the influence of E-z, D and the exchange interactions on the compensation and critical temperatures, the specific heat, the dielectric susceptibility and the internal energy of the system. Our theoretical predictions are in accordance with some experimental and theoretical results.
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| 4. |
- Bouziani, I., et al.
(författare)
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Magnetoelectronic properties of GaN codoped with (V, Mn) impurities for spintronic devices : Ab-initio and Monte Carlo studies
- 2018
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Ingår i: Physica A. - : ELSEVIER SCIENCE BV. - 0378-4371 .- 1873-2119. ; 512, s. 1249-1259
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we investigate the Magnetoelectronic properties of (V, Mn) codoped GaN using first principles calculations (FPCs) for the spintronic applications. We have obtained the ferromagnetic behavior in (Ga, V)N codoped with Mn atoms, which is believed to be caused by the double exchange mechanism. Moreover, it is observed that our system is halfmetallic at the Fermi level, with 100% spin polarization. The total magnetic moment of (V, Mn) codoped GaN is mainly originated from the V and Mn atoms, and the magnetic moment of V impurities rises with the concentration of V atoms while keeping constant that of the Mn atoms. In addition to that, the exchange coupling is obtained from FPCs and using the Ising model. The Monte Carlo method founded on the Heat Bath algorithm support our FPCs, by investigating the influence of the addition of Mn impurities to (Ga, V)N compound on the critical temperature T-C(MC), the magnetization per site M, the magnetic susceptibility chi and the specific heat C-V. We have found that T-C(MC) is above room temperature as well as the stability of the ferromagnetic state in (Ga, V)N becomes more important after the inclusion of the Manganese.
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| 5. |
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| 6. |
- Cirillo, E.N.M., et al.
(författare)
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Trapping in bottlenecks : Interplay between microscopic dynamics and large scale effects
- 2017
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Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 488:11, s. 30-38
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the appearance of trapping states in pedestrian flows through bottlenecks as a result of the interplay between the geometry of the system and the microscopic stochastic dynamics. We model the flow through a bottleneck via a Zero Range Process on a one-dimensional periodic lattice. Particle are removed from the lattice sites with rates proportional to the local occupation numbers. The bottleneck is modeled by a particular site of the lattice whose updating rate saturates to a constant value as soon as the local occupation number exceeds a fixed threshold. We show that for any finite value of the threshold the stationary particle current saturates to the limiting bottleneck rate when the total particle density in the system exceeds a critical value corresponding to the bottleneck rate itself.
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| 7. |
- El Hamri, M., et al.
(författare)
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Magnetic properties of a diluted spin-1/2 Ising nanocube
- 2016
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Ingår i: Physica A. - : Elsevier BV. - 0378-4371 .- 1873-2119. ; 443, s. 385-398
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Tidskriftsartikel (refereegranskat)abstract
- The effective-field theory with correlations based on the probability distribution technique is used to investigate the magnetic properties of a diluted Ising nanocube consisting of a ferromagnetic spin-1/2 core which is interacting antiferromagnetically with a ferromagnetic spin-1/2 surface shell. The effect of the concentration of magnetic atoms is examined. A number of interesting phenomena have been found such as the existence of the compensation temperature and triple hysteresis loops.
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| 8. |
- He, He, et al.
(författare)
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Exploring community structure in networks by consensus dynamics
- 2016
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Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 450, s. 342-353
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the relationship between community structure and consensus dynamics in complex networks. We analyze the dynamical process towards consensus and show that those sets of densely interconnected nodes corresponding to well-defined communities appear in different time scales. In order to reveal such topological scales, two algorithms built around the idea of visualizing the evolution of different measured quantities are proposed. Then we test our algorithms on a few benchmark graphs whose community structures are already known. Numeric simulations are given to demonstrate the effectiveness and reliability of our methods.
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| 9. |
- Jaksic, V., et al.
(författare)
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Estimation of nonlinearities from pseudodynamic and dynamic responses of bridge structures using the Delay Vector Variance method
- 2016
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Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 441, s. 100-120
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Tidskriftsartikel (refereegranskat)abstract
- Analysis of the variability in the responses of large structural systems and quantification of their linearity or nonlinearity as a potential non-invasive means of structural system assessment from output-only condition remains a challenging problem. In this study, the Delay Vector Variance (DVV) method is used for full scale testing of both pseudo-dynamic and dynamic responses of two bridges, in order to study the degree of nonlinearity of their measured response signals. The DVV detects the presence of determinism and nonlinearity in a time series and is based upon the examination of local predictability of a signal. The pseudo-dynamic data is obtained from a concrete bridge during repair while the dynamic data is obtained from a steel railway bridge traversed by a train. We show that DVV is promising as a marker in establishing the degree to which a change in the signal nonlinearity reflects the change in the real behaviour of a structure. It is also useful in establishing the sensitivity of instruments or sensors deployed to monitor such changes.
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| 10. |
- Jiang, Bin, 1965-
(författare)
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A complex-network perspective on Alexander's wholeness
- 2016
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Ingår i: Physica A. - : Elsevier BV. - 0378-4371 .- 1873-2119. ; 463, s. 475-484
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Tidskriftsartikel (refereegranskat)abstract
- The wholeness, conceived and developed by Christopher Alexander, is what exists to some degree or other in space and matter, and can be described by precise mathematical language. However, it remains somehow mysterious and elusive, and therefore hard to grasp. This paper develops a complex network perspective on the wholeness to better understand the nature of order or beauty for sustainable design. I bring together a set of complexity-science subjects such as complex networks, fractal geometry, and in particular underlying scaling hierarchy derived by head/tail breaks — a classification scheme and a visualization tool for data with a heavy-tailed distribution, in order to make Alexander’s profound thoughts more accessible to design practitioners and complexity-science researchers. Through several case studies (some of which Alexander studied), I demonstrate that the complex-network perspective helps reduce the mystery of wholeness and brings new insights to Alexander’s thoughts on the concept of wholeness or objective beauty that exists in fine and deep structure. The complex-network perspective enables us to see things in their wholeness, and to better understand how the kind of structural beauty emerges from local actions guided by the 15 fundamental properties, and in particular by differentiation and adaptation processes. The wholeness goes beyond current complex network theory towards design or creation of living structures.
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