28 research outputs found
Dynamic Modeling of Autorotation for Simultaneous Lift and Wind Energy Extraction
The goal of this thesis is to develop a multi-body dynamics model of autorotation with the objective of studying its application in energy harvesting. A rotor undergoing autorotation is termed an Autogyro. In the autorotation mode, the rotor is unpowered and its interaction with the wind causes an upward thrust force. The theory of an autorotating rotorcraft was originally studied for achieving safe flight at low speeds and later used for safe descent of helicopters under engine failure. The concept can potentially be used as a means to collect high-altitude wind energy. Autorotation is inherently a dynamic process and requires detailed models for characterization. Existing models of autorotation assume steady operating conditions with constant angular velocity of the rotor. The models provide spatially averaged aerodynamic forces and torques. While these steady-autorotation models are used to create a basis for the dynamic model developed in this thesis, the latter uses a Lagrangian formulation to determine the equations of motion. The aerodynamic effects on the blades that produce thrust forces, in-plane torques, and out-of-plane torques, are modeled as non-conservative forces within the Lagrangian framework. To incorporate the instantaneous aerodynamic forces, the above-mentioned spatial averaging is removed. The resulting model is causal and consists of a system of differential equations. To investigate the dynamics under energy-harvesting operation, an additional in-plane regenerative torque is added to simulate the effect of a generator. The aerodynamic effects of this regenerative braking is incorporated into the model. In addition, the dynamic model relaxes assumptions of small flapping angles, and the periodic flapping behavior of the blades are naturally generated by the dynamics instead of assuming Fourier expansions. The dynamic model enables the study of transients due to change in operating conditions or external influences such as wind speeds. It also helps gain insight into force and torque fluctuations. Model verification is conducted to ensure that the dynamic model produces similar steady-operating conditions as those reported in prior works. In addition, the behavior of autorotation under energy harvesting is evaluated. The thesis also explores the viability of achieving sufficient lift while extracting energy from prevailing winds. A range of regenerative torques are applied to determine the optimal energy state. Finally, a complete high-altitude energy harvesting system is modeled by incorporating a tether utilizing a catenary model. Overall, the thesis lends support to the hypothesis that a tethered autogyro can support its weight while harvesting energy from strong wind-fields, when augmented with appropriate control systems
Plasmodium knowlesi in Human, Indonesian Borneo
Plasmodium knowlesi is now established as the fifth Plasmodium species to cause malaria in humans. We describe a case of P. knowlesi infection acquired in Indonesian Borneo that was imported into Australia. Clinicians need to consider this diagnosis in a patient who has acquired malaria in forest areas of Southeast Asia
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Education and National Development
The New England Regional Meeting of the Comparative and International Education Society was held on the campus of Springfield College on April 29, 1977. The Conference was co-sponsored by the Division of Community Education, Springfield College, and the Center for International Education, University of Massachusetts.
The theme of the conference was Education and National Development. The papers delivered ranged in topics from a global perspective to the use of ethnic and multicultural education to assist in national development. Case studies of specific cultural areas highlight the conference. The papers provided a format for discussing and recording the experiences and research endeavors of the participants. A total of fourteen papers were delivered.
This publication contains the papers delivered at the Conference
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Virtual process capability
The quality cost of non-conformance associated with first run production builds is typically more than five times that of later production runs. If a manufacturing organization is to gain market share and increase its profitability, it must explore methods of accelerating its learning curves through defect prevention. Current Transition to Production concept methodologies attempt with limited success to accelerate organizational learning through Design for Manufacturability (DFM), design phase dimensional management studies, manufacturing floor statistical methods (SPC, DOE, etc.), and various qualitative strategies. While each of these techniques are effective to some degree in reducing future nonconformances, an integrated, design-phase approach utilizing current technology is needed. Virtual Process Capability (VPC) is a methodology for integrating statistical process capability knowledge directly into the hardware design phase, resulting in the improved performance and reduced product costs typically associated with mature product manufacturing. The intent behind the methodology is to realistically simulate the manufacture of hardware products by understanding their underlying model equations and the statistical distributions of each involved contributing parameter. Once each product has been simulated and an expected percentage defective has been estimated, mathematical programming and statistical quality engineering techniques are then utilized for improvement purposes. Data taken from the practical application of this methodology at Raytheon Aircraft has conservatively estimated that for each dollar invested ten are saved. As a technical extension to this developed methodology, statistical insights and methods are provided as to how product and process improvement analysis is best accomplished. Included within this area of discussion is the statistical development and validation of improved measures for the more efficient detection of dispersion and mean effects than that of more traditional methods. Additionally, the use of mathematical programming techniques is creatively employed as an improved mechanism in the optimization of nominal-the-best type problems
A Quantitative Energy And Systems Analysis Framework For Airborne Wind Energy Conversion Using Autorotation
The principle of autorotation could potentially be utilized for harvesting energy from strong wind fields. Autorotation is a well-known phenomenon where a rotor in a strong wind field experiences significant lift force and aerodynamic torque. With recent works indicating immense, persistent availability of wind energy at high altitudes, autorotation could be used for harvesting wind energy from such altitudes. In this paper, we build upon our previous work and implement a more detailed model of autorotation from one of the seminal works on this topic. The model is computationally challenging but yields steady operating conditions. We enhance this model by incorporating power generation in a manner that is consistent with the governing aerodynamics. This modification helps in quantifying the effects of energy harvesting on the characteristics of autorotation, a study that is not present in the literature. Furthermore, the high spatial resolution of this refined model will help in design-optimization and in control-actuation
8/2/2012 2Statistically-Based Test Optimization
Customer Success Is Our Mission is a registered trademark of Raytheon Company. The Test Optimization Challenge “We are being challenged by our customers and by the marketplace to develop and deliver increasingly complex systems with smaller performance margins that meet the user’s requirements in the shortest time, with high reliability, open and adaptable, and at the lowest cost.” Given this challenge, there is more pressure than ever on Integration, Verification & Validation activities acti ities to deliver er performance res results lts on time and within budget. Industry studies have estimated test and rework to represent between 30 and 50 % of product development costs. Given this investment, test represents fertile ground for CMMI ® high maturity optimization techniques. Typical yp benefits of statistically‐based test optimization include: – Increased Mission Assurance – Optimized performance – Improved cycle tim