Browsing by Subject "Self-organization"

Now showing 1 - 5 of 5

Open Access
Adaptability of everyday planning in urban design practices: self-organization and spontaneous action analysis of Galataport, Istanbul
(Springer Link, 2023-10-03) Korkut, C.; Nalbantoğlu, Oktan
Cities are information systems by its social and physical components. The data of these components create a wider picture in urban texture than it was designed by planners and designer in urban practices. The idea of collecting the data and composing models of spontaneous actions in urban simulations can add different dimensions to planning ideas in social terms and spatial texture. The issue is to find out how these components can be better related with each other to let citizens be urban planners as well up to some level, and what level that would be. The aim of the project is to bring back the social impact of the whole city as linking the hubs of Karaköy and Kabataş through the waterfront, also reawakening the collective memory of the port, by preserving the texture of warehouses form Ottoman Empire. The final outcome would be understanding how effectively project would be able to create the dynamics that have been proposed, and whether there have been other spontaneous actions thought the designed area.
Open Access
Adaptability of everyday planning in urban design practices: self‑organization and spontaneous action analysis of Galataport, Istanbul
(Springer, 2023-10-03) Korkut, C.; Nalbantoğlu, Oktan
Cities are information systems by its social and physical components. The data of these components create a wider picture in urban texture than it was designed by planners and designer in urban practices. The idea of collecting the data and composing models of spontaneous actions in urban simulations can add different dimensions to planning ideas in social terms and spatial texture. The issue is to find out how these components can be better related with each other to let citizens be urban planners as well up to some level, and what level that would be. The aim of the project is to bring back the social impact of the whole city as linking the hubs of Karaköy and Kabataş through the waterfront, also reawakening the collective memory of the port, by preserving the texture of warehouses form Ottoman Empire. The final outcome would be understanding how effectively project would be able to create the dynamics that have been proposed, and whether there have been other spontaneous actions thought the designed area.
Open Access
Herarchically slaved multi-pulsing mode-lock dynamics
(2021-09) Choura, Aladin
Passive mode-locking is the self-assembly of optical energy in a laser cavity to-wards narrow pulses. Often, the energy available in the cavity goes into multiple coexisting pulses with little control on their number, their energies, or their tem-poral positions. This phenomenon is vaguely known as pulse energy quantization and has been anecdotally linked to pulse splitting induced by optical nonlinear-ity. Research has focussed mainly on avoiding pulse energy quantization and any complex behavior associated with it while driving the pulses to higher and higher energies. The complex multi-pulsing behavior is often regarded as an output of a black box ﬁlled with complex nonlinear dynamics with little hope to control it. There’s a want for a clear and workable understanding of these dynamics. The central point of this thesis is that standard, few-dimensional, nearly de-terministic nonlinear dynamics oﬀers this understanding; while mode-locking is indeed the result of noisy interactions of thousands of optical modes shaping the optical pulses, due to fast pulse-shaping processes involved in mode-locking, the pulse shapes tend to be slaved to one or few order parameters, mainly the pulse energy. Then, the complex behavior is understood as the result of a much simpler nonlinear dynamical system. This understanding is supported by our experiments on a multi-pulsing Mamyshev oscillator, and in return, it guides us towards re-liably controlling it. With this control, multiple pulsation, which has been little more than a scientiﬁc curiosity, becomes technologically valuable for applications such as ablation-cooled material removal and frequency metrology. First, we address the issue of multiple pulsation. We deﬁne an energy map which describes the evolution of each pulse. Using the energy map, we show that stable coexistence of multiple pulses is permitted despite their competition on the gain if the growth of a pulse is self-limiting, i.e., if the energy map features a stable ﬁxed point even at a constant gain. The energy map similarly explains the intimately related phenomena of period-doubling, non-identical pulses, and response to perturbations. The physical processes leading to these phenomena in our laser and others are discussed in parallel, and analogies to other systems are drawn. Many attractors are permitted by the energy map, highlighting the eﬀect of bifurcations, hysteresis, and kinetics of pulse formation. Accordingly, we present guidelines for the control of multi-pulsing lasers and a procedure to control the number of pulses in a Mamyshev oscillator. Having controlled the number of pulses, we turn our attention to the temporal organization they take. Pulses coexisting in a laser cavity tend to evolve towards stable patterns due to long-range interactions between them. Several interaction mechanisms have been proposed in the literature, but the pulse interactions are still poorly understood. This is due partially to the multitude of possible inter-action mechanisms and partially to the focus of their discussion on the physical processes that allow the pulses to interact without analyzing the dynamics that result from these interactions. We argue that the temporal organization dynamics is slaved and present the form of the dynamical system for all long-ranged inter-action mechanisms and use it to derive for the ﬁrst time the stability criterion for harmonic mode-locking. A comparison between the interaction mechanisms sug-gests the dominance of acoustically mediated interactions in our oscillator. We show theoretically that the acoustic eﬀect is coupled to the single-pulse evolution dynamics and inﬂuences the individual pulse energies, which in turn, slave their speeds. This is a distinguishing feature of pulse interactions in our oscillator. We show experimentally that these interactions permit multiple stable ﬁxed points for a given number of pulses and demonstrate noise-induced transitions as well as bifurcation based on parameters of single-pulse mode-lock dynamics, conﬁrm-ing our interaction theory. Lastly, we demonstrate drastic manipulation of the acoustic interactions using a novel secondary loop, allowing richer pulse patterns, and further supporting our interactions theory.
Open Access
Logistic cellular automata
(2019-09) Ibrahimi, Muhamet
Cellular Automata (CA), initially formalized to investigate self-reproducing constructions, are among the most frequently used tools to model and understand complex systems. These computational frameworks are de ned in discrete spacetime- state domains, where time evolution occurs through local interactions. Despite the simple properties and the succinct absence of long range connections, these implementations have been proven proper for studying large scale collective behavior and self-organizing mechanisms which often emerge in dynamical systems. Following the spirit of the well-known Logistic Map, we introduce a single parameter that tunes the dynamics of totalistic CA by mapping their discrete state space into a Cantor set. By introducing this simple approach on two archetypal models, this study addresses further investigation of several complex phenomena: critical deterministic phase transitions, pattern formation and tunable emanation of self-organized morphologies in these discrete domains. We rst apply this approach to Conway's Game of Life and observe sudden changes in asymptotic dynamics of the system accompanied by emergence of complex propagators. Incorporation of the new state space with system features is used to explain the critical points and formulate the tuning parameter range where the propagators adaptively survive, by investigating their autocatalytic local interactions. Similar behavior is present when the same recipe is applied to Rule 90, a totalistic elementary one-dimensional CA. In addition, the latter case shows that transitions between Wolfram's universality classes of CA can be achieved by tuning a single parameter continuously. Finally, we implement the same idea in other models and qualitatively report the expanding complexity that these frameworks support.
Open Access
Spatial and temporal symmetry breaking in nonlinear laser lithography
(2023-01) Bin Aamir, Abdullah
Symmetry breaking is ubiquitous in nonlinear systems. This is also the case for Nonlinear Laser Lithography (NLL), in which an ultrafast laser beam incident on a material surface causes the infinite fold rotational symmetry of the material surface to be broken. In the case of linear polarization, line like structures are obtained that possess 2-fold rotational symmetry. We discuss two types of NLL, one due to the formation of oxide structures (Oxidation NLL) and the other due to material ablation (Ablation NLL). The existence of both types of structures is known for many years, however, although the regularity of oxidative structures has been significantly improved by our group earlier, the same was not true for ablative structures. Here, using the technique for Oxidation NLL and the parameters for ablative structures, we were able to achieve highly regular ablative structures which we call Ablation NLL. We demonstrate the coexistence of these two NLL structures on the same surface and how a plane can be tiled using them. Furthermore, we explore the phase space of NLL and determine the regions of the phase space occupied by the two NLL structures. We also demonstrate the versatility of NLL by obtaining Oxidation and Ablation NLL structures on several metals as well as on Silicon. We also discuss temporal symmetry breaking in NLL. If the laser beam is not incident normal to the surface and is tilted towards or away from the scanning direction, it can cause the period of the NLL structures to decrease or increase respectively. One can thus discern if a video of the beam creating a pattern while scanning over the surface along a line is run forward or backward. This dependence on the scanning direction leads to temporal symmetry breaking and is reminiscent of the Doppler effect. These symmetry breakings can be important for future research in this field along with possible commercial applications, some of which we have discussed here.