Roll-induced bifurcation in ship maneuvering under model uncertainty

In this paper, a mathematical model is developed for the maneuvering motion of a naval ship and bifurcations of its equilibrium are identified in roll-coupled motion. The subject ship is a high-speed surface combatant with twin-propeller twin-rudder system. Captive model tests are conducted for the ship using planar motion mechanism. Maneuvering coefficients are calculated by polynomial curve fitting of the test data. Uncertainty distribution in the coefficients is assumed same as that of the curve fitting errors. Uncertainty in the model coefficients is propagated to full-scale simulation results by the stochastic response surface method (SRSM). This method is computationally efficient as compared to standard Monte Carlo simulation technique. The SRSM uses polynomial chaos expansion of orthogonal to fit any probability distribution. Bifurcation analysis of the mathematical model is performed by varying the vertical center of gravity as the bifurcation parameter. Hopf bifurcation is identified. It is found that the bifurcations occur due to the coupling of roll motion with sway, yaw motion and rudder angle. In the presence of wind, roll angle response in bifurcation diagram is discussed.     

Sustainable urbanization using high speed rail (HSR) in Karnataka,India

Considering the present trends of urbanization and motorization in India, there is an urgent need for integration, revitalization and renewal of the smaller towns and cities to make urban areas in India more sustainable. Unless our regional space is reorganized to upgrade development of towns and cities and integrate them with each other and the larger cities, the urbanization process in India will become unsustainable. It is argued that High Speed Rail (HSR) can play a role in achieving this more balanced and sustainable development of towns and cities, opening up opportunities for growth across a wider, inter-connected, region, with the benefit of taking the pressure of the larger cities to absorb additional burgeoning populations. This paper will make the case that in the current Indian context, current patterns of mega-city growth are unsustainable, and that HSR can play an important role in providing opportunities for medium and smaller size cities through their interconnections. It begins by highlighting the role that railways have played in India and other countries, noting that merely economic analysis of their costs and benefits generally underestimated their contributions to development. It then provides an introduction to HSR and its potential impact in general, before applying this to the example of the State of Karnataka in South India.