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Dynamics of Ferrofluidic Flow in the Taylor-Couette System With a Small Aspect Ratio

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We investigate fundamental nonlinear dynamics of ferrofluidic Taylor-Couette flow - flow confined be-tween two concentric independently rotating cylinders - consider small aspect ratio by solving the ferro-hydrodynamical equations, carrying out systematic bifurcation analysis. Without magnetic field, we find steady flow

We investigate fundamental nonlinear dynamics of ferrofluidic Taylor-Couette flow - flow confined be-tween two concentric independently rotating cylinders - consider small aspect ratio by solving the ferro-hydrodynamical equations, carrying out systematic bifurcation analysis. Without magnetic field, we find steady flow patterns, previously observed with a simple fluid, such as those containing normal one- or two vortex cells, as well as anomalous one-cell and twin-cell flow states. However, when a symmetry-breaking transverse magnetic field is present, all flow states exhibit stimulated, finite two-fold mode. Various bifurcations between steady and unsteady states can occur, corresponding to the transitions between the two-cell and one-cell states. While unsteady, axially oscillating flow states can arise, we also detect the emergence of new unsteady flow states. In particular, we uncover two new states: one contains only the azimuthally oscillating solution in the configuration of the twin-cell flow state, and an-other a rotating flow state. Topologically, these flow states are a limit cycle and a quasiperiodic solution on a two-torus, respectively. Emergence of new flow states in addition to observed ones with classical fluid, indicates that richer but potentially more controllable dynamics in ferrofluidic flows, as such flow states depend on the external magnetic field.

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2017-01-06

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Handling solid and hazardous waste by waste pickers: a case study of Phnom Penh, Cambodia

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The handling of waste encompasses the following processes: recycling, collection, treatment, and disposal. It is crucial to provide a cost-effective waste management system that improves public health and reduces environmental risks. In developing countries, proper handling of solid and hazardous

The handling of waste encompasses the following processes: recycling, collection, treatment, and disposal. It is crucial to provide a cost-effective waste management system that improves public health and reduces environmental risks. In developing countries, proper handling of solid and hazardous wastes remain severely limited in urban cities if the industries and hospitals producing it do not take responsibility. Recycling and reusing of 12% of total waste in Phnom Penh is an active industry in Cambodia, driven by an informal network of waste pickers, collectors, and buyers. This thesis examines the environmental situation of solid and hazardous wastes in Phnom Penh. The socio-economic background of waste pickers and their current practices for handling solid and hazardous wastes will be mainly discussed in order to understand health and sanitation impacts and risks for disposal of solid and hazardous waste by these informal waste pickers. Surveys and interviews with the following sources are conducted: waste pickers, community members, observation at local dumpsites, governmental officials, and other non-government organization agencies in Phnom Penh, Cambodia. This thesis reports the external and internal factors that hinder safety and cost-effective management for disposal of solid and hazardous wastes. Multiple literature reviews are assessed in regards to the health effects, economic, and social impacts in developing countries. Evidentially, after attending several training and environmental awareness-raising programs, waste pickers expressed concerns about their health and the environment. Instead of receiving support, waste pickers are under economic pressure to use improper tools for waste picking, to stop working, get access to health care/service, to change their career, and prevent contact to limit serious communicable diseases and disability. As a result, the government and other related government agencies have made an effort to establish sanitation handling, treatment, and disposal systems by closing the old dumpsite. Due to limited entrepreneurship and business experience after training, most waste pickers cannot initiate micro business or find new jobs and then resume their waste picking. In conclusion, this thesis proposed that there are alternative technologies and management methods that will allow waste pickers to maintain employment while minimizing hazardous waste. Some examples of alternatives for waste pickers are establishing a material recovery center and alternative higher income occupation.

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2012