Stabilization of aerodynamically excited turbomachinery with hydrodynamic journal bearings and supports

A method of analyzing the first mode stability and unbalance response of multimass flexible rotors is presented whereby the multimass system is modeled as an equivalent single mass modal model including the effects of rotor flexibility, general linearized hydrodynamic journal bearings, squeeze film bearing supports and rotor aerodynamic cross coupling. Expressions for optimum bearing and support damping are presented for both stability and unbalance response. The method is intended to be used as a preliminary design tool to quickly ascertain the effects of bearing and support changes on rotor-bearing system performance

Collective performance of a finite-time quantum Otto cycle

We study the finite-time effects in a quantum Otto cycle where a collective spin system is used as the working fluid. Starting from a simple one-qubit system we analyze the transition to the limit cycle in the case of a finite-time thermalization. If the system consists of a large sample of independent qubits interacting coherently with the heat bath, the superradiant equilibration is observed. We show that this phenomenon can boost the power of the engine. Mutual interaction of qubits in the working fluid is modeled by the Lipkin-Meshkov-Glick Hamiltonian. We demonstrate that in this case the quantum phase transitions for the ground and excited states may have a strong negative effect on the performance of the machine. Reversely, by analyzing the work output we can distinguish between the operational regimes with and without a phase transition.Comment: 13 pages, 11 figure

Modeling a Grid-Connected PV/Battery Microgrid System with MPPT Controller

This paper focuses on performance analyzing and dynamic modeling of the current grid-tied fixed array 6.84kW solar photovoltaic system located at Florida Atlantic University (FAU). A battery energy storage system is designed and applied to improve the systems stability and reliability. An overview of the entire system and its PV module are presented. In sequel, the corresponding I-V and P-V curves are obtained using MATLAB-Simulink package. Actual data was collected and utilized for the modeling and simulation of the system. In addition, a grid- connected PV/Battery system with Maximum Power Point Tracking (MPPT) controller is modeled to analyze the system performance that has been evaluated under two different test conditions: (1) PV power production is higher than the load demand (2) PV generated power is less than required load. A battery system has also been sized to provide smoothing services to this array. The simulation results show the effective of the proposed method. This system can be implemented in developing countries with similar weather conditions to Florida.Comment: 6 pages, 14 figures, PVSC 201

THE ROLE OF TECHNOLOGY IN THE BUILT ENVIRONMENT

Lately, the built environment has been witnessing a lot of hazards ranging from collapsed buildings and bridges, floods and typhoons, droughts and landslides, as well as fire, tsunamis, hurricanes and earthquakes. Others are hazards launched through technology such as bio-terrorism and cyber-terrorism. Thus, necessity is place on Architecture, Engineering and Construction (AEC) industry to prevent the "sick building" syndrome and make the built environment safe, secure, and healthy for mankind. This paper attempts to examine the immediate and remote causes of fail and sick buildings with a view to proffering solutions through the use of technology. Furthermore, the paper presents the application of the available technologies such as e-construction, Geographical Information System (GIS), Computer Aided Design (CAD) and the Global Positioning System (CPS) to the built environment. An integrated design environment within the AEC industry is proposed to allow for modeling, designing, analyzing, and visualizing structures. Thus, the behaviour of structures can be modeled through "virtual reality", leading to the creation of "smart buildings", which are design concepts for this generation