جستجوی مقالات مرتبط با کلیدواژه "chaos" در نشریات گروه "فیزیک"

In this paper, the behavior of the double pendulums has been studied by considering the effect of initial conditions (angular displacement of the outer pendulum for four cases 12, 30, 90, and 150 degrees) and the influence of system geometry (increasing rod length and mass of the second pendulum), also. After extracting motion equations using the Lagrangian method, in order to deal with the frequency spectrum, traces of bobs, and understanding the system behavior for every case, the Fast Fourier Transform (FFT) technique and Poincare sections have been applied. The obtained results show that the consequence of the rising angular displacement the outer pendulum is to increase the energy level of the system and the change of its behavior from quasi-periodic for angular displacement is less than 90 degrees to chaotic when it is 150 degrees. Therefore, the energy level, in this case, has increased more than twice compared to the first. In addition, it seems a quasi-periodic behavior is forming at the heart of chaotic behavior. On the other hand, the results indicate a very significant effect of geometrics on a system's behavior. According to the calculations, the consequence of increasing the length of the rod of the second pendulum has only led to a different behavior from its similar case (case number 3) completely. however, their energy level is the same. Increasing the mass of the outer by twice not only to lead decrease energy level of the system by 330J but also has shown chaotic behavior (in comparison to the case3).

We consider two nonlinear electrical circuits consisting of two nonlinear capacitors that are coupled to each other through linear inductors (mutual induction) under the influence of time-dependent external fields. By excitation of two non-linear chaos  electrical circuits (chaos oscillators) by each other, the Lyapunov indexes were extracted numerically and the synchronization of two electrical circuits without chaos connection was observed. The dependence of  the Lyapunov exponent on the numerical value of the coupling coefficient (mutual induction m) has been studied and the critical value of this coefficient has been determined. Also, the effect of this coupling coefficient of two nonlinear electrical circuits (two Duffing oscillators) coupled without connection has been investigated in order to observe different dynamic states. Diagrams of charge and current changes in terms of time for the numerical value of critical mutual induction have been studied and the synchronization of the two circuits is shown.

This paper investigates the stochastic heating of electrons caused by Raman backscatter radiations during the interaction of a laser pulse with helium atoms by means of a parallel particle-in-cell (PIC) code. At different propagation times, the self-consistent laser pulse changes are investigated via the space-time Fourier transform of the transverse vector potential. It is demonstrated that, since ionization has a striking influence on the emission of Raman backscattered radiation, it also plays an important role in the threshold of electron stochastic heating. As demonstrated by the experiments, the Raman backscattered radiations are initiated by a strong initial noise when a laser pulse has a long rise time, 100 fs. Hence, the fundamental condition for the chaos threshold is satisfied sooner by examining ionization effects. In this manner, stochastic heating of the electrons is initiated more rapidly than if the laser pulse were emitted in the preplasma. Accordingly, in concurrence with the idea of chaos, the electrons acquire more energy via the stochastic mechanism in the field-ionized plasma.

Fault and fracture modelling is an important step in reservoir engineering which is required for any reservoir characterization and production management. There are various types of methods and strategies for building such models, however, each has its own advantages and drawbacks. The most important issue that should be considered is the ability to model both large- and small-scale faults, simultaneously. It is important, as large faults define geological frameworks of the reservoir, while small faults influence fluid movement in the reservoir. In this study, we introduce an integrated strategy for modelling small- and large-scale faults by seismic data, using multi-attributes. Large faults are defined by hand picking from seismic data using attributes, and small faults are modelled by an automatic ant tracking algorithm. Then, two separated models are integrated to build a unique, but multi-scale fault model. Result of each step of modelling is evaluated by well data. The methodology is applied on a hydrocarbon reservoir from the Persian Gulf. Results show that the multi scale fault model is accurate when evaluated by well data. Integrated modelling of faults of fractures to obtain a unique multi-scale model is an interesting topic in reservoir engineering. Normally fractured reservoirs are divided into several production zones based on division made by large faults, while fluid movement in each zone is controlled by small fracturs and faults. Thus, obtaining a unique model which contain information of faults in several scale is under investigation. However, conventional methods use separate sources of information for modelling faults in various scales. Large scale faults are normally modelled by seismic data while well data are used for modelling small faults. Ozkaya (2019) stated that modelling of faults both with seismic and well data would reduce uncertainty in reservoir fracture modelling. Cao et al. (2019) introduced an integrated strategy for modeling faults with two scales in 2D seismic data, but using seismic and well data. Kurison et al. (2019) have modelled faults and fractures in reservoir with 3D seismic data and well data, but in separate manners. But their final interpretation has shown that using both types of model would result in better reservoir modelling. Xu et al. (2019) introduced an integrated strategy for modelling faults and fractures in two scales simultaneously using seismic and well data. In this study, we introduce an integrated strategy for multi-scale fault modelling using only seismic data, which could be used in reservoirs which lack of well data. The proposed strategy introduced here, initiates with a geological model building. Subsequently, large faults can be defined on seismic data and related attributes. Simultaneously, small scale faults can be modelled by an ant tracking algorithm in an automatic manner, then it would be refined by interpreter to remove other lineaments than fault that was modelled by the algorithm. Each model then would be evaluated by well data and in case of any error in the model, they would be removed by more ant tracking parameter optimizations and also deeper investigation by the interpreter. In the final step, both fault model would be integrated to build a unique informative multi-scale fault model which contains information of all faults in various sizes. Other characteristics of faults in the integrated model would be investigated for further analysis. Large scale fault model showed major faults with northwest-southeast trending acting in the center of the reservoir, which has a dome shaped structure, and some minor faults with various trending around the major one. Through this modeling curvature, chaos and variance attributes were used for better fault detection. Small faults obtained by ant tracking distributed around the center of the field. Ant tracking algorithm parameter were optimized through sensitivity analysis prior to application. Afterwards, fault model was refined to remove non-fault lineament. Both models were evaluated by a fullbore formation microimager (FMI) log which proved fractures and faults that were obtained by seismic data. One fault that was detected by the proposed strategy were also captured by well. Then both fault models were integrated to a unique model and faults were modeled by deterministic method. The integrated fault model obtained by the proposed strategy revealed the importance of a multi-scale fault model in reservoir engineering. Large faults of the study reservoir showed different zones of fractures in the formation reservoir, while small faults in the same model built a discrete network of fractures which provides canals for fluid movement. The integrated model shows that large faults in the study field are mostly in the center of the reservoir, while small faults are distributed through the edges of the formation reservoir, which could be used for further investigation of locating for production and/or injection wells.

There are several methods to synchronize chaotic systems. In this work, we have proposed the adaptive synchronization to study the three interesting systems. These systems are Rössler-Rössler, Liu-Liu, and Liu-Rössler. We have simulated the synchronization of the systems under different circumstances. A numerical simulation of synchronization between the proposed systems demonstrates that the systems can synchronize with this method perfectly even in the presence of unknown parameters. We have deduced that the synchronization speed in the first system (Rössler-Rössler) is faster than the rest. Also, the second system (Liu-Liu) is synchronized faster than the third system. According to the results obtained in this paper, we can say that the adaptive synchronization works better on similar systems such as Rössler-Rössler and Liu-Liu.