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Browsing by Author "Chen, Shuo"

Now showing 1 - 3 of 3
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    Analysis and wave tank verification of the performance of point absorber WECs with different configurations
    Li, Xiaofan; Martin, Dillon; Jiang, Boxi; Chen, Shuo; Thiagarajan, Krish; Parker, Robert G.; Zuo, Lei (2021-10)
    Extracting energy from ocean waves has become a heated topic since the energy crisis of the 2000s. Among all the different concepts and designs of Wave Energy Converter (WEC), point absorber is a widely adopted type with great potential, and various configurations and constraints are applicable to it. Here, the point absorber WECs with four different set-up configurations are explored: single body heaving WEC, two-body heaving WEC, two-body WEC with a flat plate (Reference Model 3), and a two-body WEC with a cylinder-shaped second body. Dynamic models are established for each case and wave tank tests are conducted for verification. The results show that the power capture of a point absorber can benefit from several aspects: the two-body WEC with a streamlined shape can double the wave capture width ratio (up to 66.5%) over the single-body WEC or Reference Model 3, while coupling other motion or mooring dynamics can further improve the capture width ratio by 12% by increasing the relative motion stroke.
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    The Application of the Expectation-Maximization Algorithm to the Identification of Biological Models
    Chen, Shuo (Virginia Tech, 2006-12-11)
    With the onset of large-scale gene expression profiling, many researchers have turned their attention toward biological process modeling and system identification. The abundance of data available, while inspiring, is also daunting to interpret. Following the initial work of Rangel et al., we propose a linear model for identifying the biological model behind the data and utilize a modification of the Expectation-Maximization algorithm for training it. With our model, we explore some commonly accepted assumptions concerning sampling, discretization, and state transformations. Also, we illuminate the model complexities and interpretation difficulties caused by unknown state transformations and propose some solutions for resolving these problems. Finally, we elucidate the advantages and limitations of our linear state-space model with simulated data from several nonlinear networks.
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    Mechanical Motion Rectifier Based Single and Hybrid Input Marine Energy Harvester Analysis, Design and Basin Test Validation
    Chen, Shuo (Virginia Tech, 2021-05-19)
    Point absorber style marine energy harvesters have been investigated based on their structure, energy harvesting efficiency, and reliability along with costs. However, due to the continuously varying ocean conditions and climates, the system usually suffers low power output and reliability from low input and high Peak to Average Ratio (PAR). Therefore, a Mechanical Motion Rectifier (MMR) based point absorber is introduced in this thesis to promote the harvesting efficiency and reduce the PAR by unifying the input rotation, and allow disengagement inside the gearbox during low power output phase. A 1:20 scale full system was then designed, prototyped, and tested based on the MMR. The bench test results show that the proposed MMR based point absorber could improve the energy conversion efficiency by 10 percent, which brings feasibility to the implementation. Traditional Wave Energy Converter(WEC) can only harvest ocean waves while ocean current is also one of the significant energy sources widely existing in ocean. In order to further increase the energy harvesting efficiency, one individual energy input source shows its limits. A vast majority of places around the world tends to co-exist both marine waves and current, and extracting energy from both sources could potentially increase the electric power output. Therefore, the Hybrid Wave and Current Energy Harvester (HWCEC) is introduced along with the hybrid gearbox. It is capable of harvesting energy from both ocean waves and current simultaneously so that the electric power output is significantly higher from a combined system. Tank test data shows 38-79 percent of electric power output promotion of an HWCEC compared to a regular WEC, and 70 percent reduced PAR in irregular wave condition. After that, system electric damping has been thoroughly investigated on both electrical side and mechanical side. The best power output corresponding electrical resistance is identical to the generator internal resistance while the best gear ratio of 3.5 is determined via both simulation and tank test. Furthermore, the system's PAR has been investigated by analyzing the trend of the peak occurrence. Tank test data shows the HWCEC's output power peak occurrence is at roughly 20 percent located at its PAR average. Therefore, the HWCEC system can promote energy harvesting efficiency to the combined system design, and improve its reliability from a significantly reduced peak to average ratio. It also gives HWCEC a large variety of deployable locations compared to a regular WEC under more marine environment. Furthermore, a new design of the Hybrid model, Hybrid LITE, is then developed, which not only features the HWCEC features, but also a lightweight, immersive and inflatable design for fast deployment and transportation. Since the system is built with an open water chassis, the overall system robustness is significantly improved since no water sealing is required on the powertrain compared to the HWCEC.