A study of the rotating-stall inception in high-speed compressors

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1994.Includes bibliographical references (leaves 41-42).by Michail Tryfonidis.M.S

Power Performance and Response Analysis of a Semi-Submersible Wind Turbine Combined with Wave Energy Converters in Intermediate and Deep Water

Renewable energies are the forefront against environmental pollution and the leading technology in sustainable energy sources. Power produced by wind energy is a well established technology. There is a lot of space for expansion though, especially at offshore environment. Floating wind turbines can take advantage of the abundant wind energy available far out at the oceans. Increasing the power production of such structures and ensuring the efficient and safe position keeping of them in every depth is crucial. Two concepts that aim to tackle down these two issues are proposed. A combination of wind and wave energy converters and an intermediate water depth mooring arrangement. The installation of wave energy converters (WECs) at the floating wind turbine base will reduce the levelized cost of energy (LCoE). The use of the same power cables and mooring arrangement to deploy the WECs can prove beneficial financially wise. Furthermore, it can act as a boost to the development of wave energy in general. The transient depth between shallow and deep is a challenging field for the traditional mooring arrangements. A cost effective solution will help the deployment of floating wind turbines in this intermediate water depth fields. A novel concept of combining a floating wind turbine with WECs is proposed. A semi submersible floater is used to support a 5MW wind turbine. Three flap typed WECs are deployed on the pontoons of the floater. A two-point type absorber called Torus is installed at the central column. The proposed concept is named STFC. A thorough analysis of the natural periods, regular and irregular wave tests is performed to evaluate the effect of the WECs to the floater’s behavior. Small to no effect is observed across all degrees of freedom except the reduction in pitch period due to increased hydrostatic stiffness. The irregular wave tests indicate that the absorbed power amplitude operator (RAO) of Torus has a wider excitation range than the flaps. The floater heave RAO is affected by the addition of Torus and the floater surge and pitch RAOs are affected by the additions of flaps. Irregular waves tests are carried out to evaluate the influence of the added WECs to the motions of the combined concept and the total power performance. The results indicate that the WECs have little to no effect to the motions of the structure except the expected reduction in pitch motions. This is preliminary indication that no changes should be made to the mooring due to the addition of WECs. The wind turbine power performance is not affected by the addition of WECs. There is small reduction in pitch standard deviation though, in loading condition EC3 that leads to slightly better wind quality. The Torus performance is satisfactory as it accounts for 9% of the total STFC power production. The total three flaps account only for 14% of the Torus power production thus their power performance is not satisfactory. The flaps rotation is out of phase with the wave excitation force so there is room for improvement if active damping and stiffness control is added. Following, the STFC is moved to intermediate water depth z = -50m and a new hybrid mooring design is proposed. A brief explanation of the intermediate water mooring challenges is given and the basic design criteria are established. A step to step designing process is presented. The combination of studded chain, buoys, and clump weights is proposed. The name of the concept is CCCB. A restoring force test is carried out and the linearity of the restoring force response is verified. Irregular wave tests are carried out and the data indicate that the new mooring design is a feasible design. The maximum floater offset is restrained to 14% of the water depth. The pretension of the mooring system proves to be a significant factor for the total performance of the mooring arrangement. The maximum mooring line tension is kept within safe limits throughout the whole offset range. CCCB is compared with similar concepts and proves itself stiffer mainly because of its increased pretension. Points of interest are defined across the mooring line and spectra analysis is performed to evaluate the distribution of response frequencies across the chain length. The role of buoys as dampers of motions is established. CCCB utilization factor indicates that this mooring design can be used also in larger structures and there is room for cost reduction measures

Robust adaptive control modeling of human arm movements subject to altered gravity and mechanical loads

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1999.Includes bibliographical references (leaves 159-164).It has been observed that during orbital spaceflight the absence of gravitation related sensory inputs causes incongruence between the expected and the actual sensory feedback resulting from voluntary movements. This incongruence results in a reinterpretation or neglect of gravity-induced sensory input signals. Over time, new internal models develop, gradually compensating for the loss of spatial reference. The study of adaptation of goal-directed movements is the main focus of this thesis. The hypothesis is that during the adaptive learning process the neural connections behave in ways that can be described by an adaptive control method. The investigation presented in this thesis includes two different sets of experiments. A series of dart throwing experiments took place onboard the space station Mir. Experiments also took place at the Biomechanics lab at MIT, where the subjects performed a series of continuous trajectory tracking movements while a planar robotic manipulandum exerted external torques on the subjects' moving arms. The experimental hypothesis for both experiments is that during the first few trials the subjects will perform poorly trying to follow a prescribed trajectory, or trying to hit a target. A theoretical framework is developed that is a modification of the sliding control method used in robotics. The new control framework is an attempt to explain the adaptive behavior of the subjects. Numerical simulations of the proposed framework are compared with experimental results and predictions from competitive models. The proposed control methodology extends the results of the sliding mode theory to human motor control. The resulting adaptive control model of the motor system is robust to external dynamics, even those of negative gain, uses only position and velocity feedback, and achieves bounded steady-state error without explicit knowledge of the system's nonlinearities. In addition, the experimental and modeling results demonstrate that visuomotor learning is important not only for error correction through internal model adaptation on ground or in microgravity, but also for the minimization of the total mean-square error in the presence of random variability. Thus human intelligent decision displays certain attributes that seem to conform to Bayesian statistical games.by Michail Tryfonidis.Ph.D

Impact of Screening on Breast Cancer Mortality: The UK Program 20 Years On

This study was funded by a grant from the UK Department of Health (no. 106/0001). The grant was awarded to Prof Stephen W Duffy

70-Gene Signature as an Aid to Treatment Decisions in Early-Stage Breast Cancer.

The 70-gene signature test (MammaPrint) has been shown to improve prediction of clinical outcome in women with early-stage breast cancer. We sought to provide prospective evidence of the clinical utility of the addition of the 70-gene signature to standard clinical-pathological criteria in selecting patients for adjuvant chemotherapy. In this randomized, phase 3 study, we enrolled 6693 women with early-stage breast cancer and determined their genomic risk (using the 70-gene signature) and their clinical risk (using a modified version of Adjuvant! Online). Women at low clinical and genomic risk did not receive chemotherapy, whereas those at high clinical and genomic risk did receive such therapy. In patients with discordant risk results, either the genomic risk or the clinical risk was used to determine the use of chemotherapy. The primary goal was to assess whether, among patients with high-risk clinical features and a low-risk gene-expression profile who did not receive chemotherapy, the lower boundary of the 95% confidence interval for the rate of 5-year survival without distant metastasis would be 92% (i.e., the noninferiority boundary) or higher. A total of 1550 patients (23.2%) were deemed to be at high clinical risk and low genomic risk. At 5 years, the rate of survival without distant metastasis in this group was 94.7% (95% confidence interval, 92.5 to 96.2) among those not receiving chemotherapy. The absolute difference in this survival rate between these patients and those who received chemotherapy was 1.5 percentage points, with the rate being lower without chemotherapy. Similar rates of survival without distant metastasis were reported in the subgroup of patients who had estrogen-receptor-positive, human epidermal growth factor receptor 2-negative, and either node-negative or node-positive disease. Among women with early-stage breast cancer who were at high clinical risk and low genomic risk for recurrence, the receipt of no chemotherapy on the basis of the 70-gene signature led to a 5-year rate of survival without distant metastasis that was 1.5 percentage points lower than the rate with chemotherapy. Given these findings, approximately 46% of women with breast cancer who are at high clinical risk might not require chemotherapy. (Funded by the European Commission Sixth Framework Program and others; ClinicalTrials.gov number, NCT00433589; EudraCT number, 2005-002625-31.)

Bowing fracture of the inferior angle of the scapula, a difficult diagnosis

A 4-year-old boy presented with swelling over the inferior tip of the scapula and an unclear history. Initial radiographic findings were concerning for an aggressive lesion. This case highlights how a multimodality imaging approach was used to relieve uncertainty by diagnosing a paediatric bowing type fracture of the scapular tip