Dynamics and Pattern Formation in Large Systems of Spatially-Coupled Oscillators with Finite Response Times

We consider systems of many spatially distributed phase oscillators that interact with their neighbors. Each oscillator is allowed to have a different natural frequency, as well as a different response time to the signals it receives from other oscillators in its neighborhood. Using the ansatz of Ott and Antonsen (Ref. \cite{OA1}) and adopting a strategy similar to that employed in the recent work of Laing (Ref. \cite{Laing2}), we reduce the microscopic dynamics of these systems to a macroscopic partial-differential-equation description. Using this macroscopic formulation, we numerically find that finite oscillator response time leads to interesting spatio-temporal dynamical behaviors including propagating fronts, spots, target patterns, chimerae, spiral waves, etc., and we study interactions and evolutionary behaviors of these spatio-temporal patterns

CO2 Energy Reactor – Integrated Mineral Carbonation: Perspectives on Lab-Scale Investigation and Products Valorization

To overcome the challenges of mineral CO2 sequestration, Innovation Concepts B.V. is developing a unique proprietary gravity pressure vessel (GPV) reactor technology and has focussed on generating reaction products of high economic value. The GPV provides intense process conditions through hydrostatic pressurization and heat exchange integration that harvests exothermic reaction energy, thereby reducing energy demand of conventional reactor designs, in addition to offering other benefits. In this paper, a perspective on the status of this technology and outlook for the future is provided. To date, laboratory-scale tests of the envisioned process have been performed in a tubular “rocking autoclave” reactor. The mineral of choice has been olivine [~Mg1.6Fe2+0.4(SiO4) + ppm Ni/Cr], although asbestos, steel slags, and oil shale residues are also under investigation. The effect of several process parameters on reaction extent and product properties has been tested: CO2 pressure, temperature, residence time, additives (buffers, lixiviants, chelators, oxidizers), solids loading, and mixing rate. The products (carbonates, amorphous silica, and chromite) have been physically separated (based on size, density, and magnetic properties), characterized (for chemistry, mineralogy, and morphology), and tested in intended applications (as pozzolanic carbon-negative building material). Economically, it is found that product value is the main driver for mineral carbonation, rather than, or in addition to, the sequestered CO2. The approach of using a GPV and focusing on valuable reaction products could thus make CO2 mineralization a feasible and sustainable industrial process

The Collision of Two Black Holes

We study the head-on collision of two equal mass, nonrotating black holes. We consider a range of cases from holes surrounded by a common horizon to holes initially separated by about $20M$, where $M$ is the mass of each hole. We determine the waveforms and energies radiated for both the $\ell = 2$ and $\ell=4$ waves resulting from the collision. In all cases studied the normal modes of the final black hole dominate the spectrum. We also estimate analytically the total gravitational radiation emitted, taking into account the tidal heating of horizons using the membrane paradigm, and other effects. For the first time we are able to compare analytic calculations, black hole perturbation theory, and strong field, nonlinear numerical calculations for this problem, and we find excellent agreement.Comment: 14 pages, 93-

Nonlinear r-Modes in Neutron Stars: Instability of an unstable mode

We study the dynamical evolution of a large amplitude r-mode by numerical simulations. R-modes in neutron stars are unstable growing modes, driven by gravitational radiation reaction. In these simulations, r-modes of amplitude unity or above are destroyed by a catastrophic decay: A large amplitude r-mode gradually leaks energy into other fluid modes, which in turn act nonlinearly with the r-mode, leading to the onset of the rapid decay. As a result the r-mode suddenly breaks down into a differentially rotating configuration. The catastrophic decay does not appear to be related to shock waves at the star's surface. The limit it imposes on the r-mode amplitude is significantly smaller than that suggested by previous fully nonlinear numerical simulations.Comment: Published in Phys. Rev. D Rapid Comm. 66, 041303(R) (2002

Suppression and Enhancement of Soliton Switching During Interaction in Periodically Twisted Birefringent Fiber

Soliton interaction in periodically twisted birefringent optical fibers has been analysed analytically with refernce to soliton switching. For this purpose we construct the exact general two-soliton solution of the associated coupled system and investigate its asymptotic behaviour. Using the results of our analytical approach we point out that the interaction can be used as a switch to suppress or to enhance soliton switching dynamics, if one injects multi-soliton as an input pulse in the periodically twisted birefringent fiber.Comment: 10 pages, 4 figures, Latex, submitted to Phys. Rev.

Evaluating The Effects of Signal Control Applications on Roundabout’s LOS Performance Using VISSIM Microsimulation Model

The existence of unbalanced and high traffic flows at roundabout have resulted in poor performance and safety concerns. Past research has shown that applications of signal control at problematic roundabouts had significantly improved its Level of Service (LOS) performance. This study investigates the effects of different signal phasing plans on the roundabout’s LOS performance using VISSIM microsimulation model. The findings revealed that both Approach-Signal-Control Roundabout ACSR and Two-Stop-Line Control Signalized Roundabout TSLSR signal phasing methods did not significantly improve the roundabout’s entry capacities. Partial signal control applications, however, have resulted in a significant reduction in vehicle delays and higher entry capacities. The results of this study provide a good overview to local traffic practitioners on how to evaluate and implement the signal control strategy at problematic roundabouts. &nbsp

Evaluating The Effects of Signal Control Applications on Roundabout’s LOS Performance Using VISSIM Microsimulation Model

The existence of unbalanced and high traffic flows at roundabout have resulted in poor performance and safety concerns. Past research has shown that applications of signal control at problematic roundabouts had significantly improved its Level of Service (LOS) performance. This study investigates the effects of different signal phasing plans on the roundabout’s LOS performance using VISSIM microsimulation model. The findings revealed that both Approach-Signal-Control Roundabout ACSR and Two-Stop-Line Control Signalized Roundabout TSLSR signal phasing methods did not significantly improve the roundabout’s entry capacities. Partial signal control applications, however, have resulted in a significant reduction in vehicle delays and higher entry capacities. The results of this study provide a good overview to local traffic practitioners on how to evaluate and implement the signal control strategy at problematic roundabouts. &nbsp