Calculation of Weibull strength parameters, Batdorf flaw density constants and related statistical quantities using PC-CARES

This manual describes the operation and theory of the PC-CARES (Personal Computer-Ceramic Analysis and Reliability Evaluation of Structures) computer program for the IBM PC and compatibles running PC-DOS/MS-DOR OR IBM/MS-OS/2 (version 1.1 or higher) operating systems. The primary purpose of this code is to estimate Weibull material strength parameters, the Batdorf crack density coefficient, and other related statistical quantities. Included in the manual is the description of the calculation of shape and scale parameters of the two-parameter Weibull distribution using the least-squares analysis and maximum likelihood methods for volume- and surface-flaw-induced fracture in ceramics with complete and censored samples. The methods for detecting outliers and for calculating the Kolmogorov-Smirnov and the Anderson-Darling goodness-of-fit statistics and 90 percent confidence bands about the Weibull line, as well as the techniques for calculating the Batdorf flaw-density constants are also described

Stability and Dynamic Properties of Tip Vortices Shed from Flexible Rotors of Floating Offshore Wind Turbines

Floating offshore wind turbines exhibit unique near-wake characteristics due to ocean wave-induced rigid body motion of their rotor. The unique near-wake properties of this wind turbine are studied numerically as a coupled fluid-structure interaction (aeroelastic) phenomenon. The near-wake aerodynamics are modeleld in a Lagrangian sense by the lifting-line free-vortex wake method, and the dynamic rotor-blade structural deformations are described by the beam theory of spinning structures. The aerodynamic and structural domains are strongly coupled using a relaxation and subiteration scheme at each time step. This aeroelastic framework is believed to be the first of its kind with regards to its applications in studying floating offshore wind turbines. A linear eigenvalue stability analysis is used to evaluate the near-wake dynamics and the stability of the wake generated by the aeroelastic simulations. The stability analysis serves as a quantification tool of vortex reactions (divergence rates) and dynamics due to arbitrary disturbances, such as gusts, incoming turbulence, and blade deformation.The aeroelastic framework is validated against below-rated, rated, and above-rated onshore aeroelastic operational conditions of the NREL 5MW reference wind turbine and is compared against rigid rotor simulations. The numerical result highlight qualitatively the difference between wakes generated by rigid and flexible rotors, and indicate the flexible rotors tend to generate more unstable wakes, which lead to earlier wake breakdowns. Aeroelastic simulations indicated that rotor performance metrics, such as rotor power, torque, and thrust, are impacted by the dynamic rotor-blade structural deformations due to the effect blade dynamics have on pressure and velocity deficits across the rotor plane. Simulations of the floating offshore wind turbine operational cases highlight the level of impact that the offshore environment has on the rotor blade dynamics, rotor thrust, rotor power, and rotor torque. Specifically, results show that the offshore environment at below-rated cases provides quasi-static wave-induced motions of the rotor that marginally affect the rotor performance metrics. Rated and above-rated offshore conditions, however, show clear and notable impact on rotor performance, such that performance metrics fluctuate at the frequency of the wave-induced rotor motion.The stability analyses conducted on wakes generated by onshore (fixed) rotors show that divergence-rates of near-wakes fluctuate in time at a rate inversely proportional to the rotor rotation frequency. It is found that the wave-induced motion of the offshore environment breaks this stability trend and causes periodic divergence-rate fluctuations that oscillate under the influence of the wave-induced motion of the turbine. Finally, it is found that blade vibrations introduce higher frequency content in the divergence rate fluctuation in time. However, the dynamic blade deformations dampen the divergence rate fluctuation amplitudes

Development of Functional Requirements for a High-capacity Airspace System

NASA along with other researchers visualizes a future where more aircraft will transport passengers or goods around the world. Thus, they envision increasing air capacity from 10 to 100 times more than the current system without any reduction in efficiency or safety. Many models are being proposed that comply with the necessary requirements to form part of the method needed. However, knowing which of the proposed methods have the most desirable characteristics, such as efficiency and safety, are yet to be determined. For this reason, a standardized method to compare and assess them has to be developed, since is not possible to apply them all. An approach to this issue is establishing functional requirements, which are a set of standards that assess and compare performances of new models. Thus, this research is focused on identifying quality measures, which are measures of the requirements, in order to establish functional requirements. As for the first step, measures regarding air transportation system were collected and analyzed by literature review and surveys to determine the potential candidates. As a result, the final potential quality measure candidates were obtained that lead us to determine the ideal measures of the functional requirements and three types of quality measures were discovered. These measures of the functional requirements will constitute a standard to assess new models being proposed and determine the most desirable results

Brachial Artery Constriction during Brachial Artery Reactivity Testing Predicts Major Adverse Clinical Outcomes in Women with Suspected Myocardial Ischemia: Results from the NHLBI-Sponsored Women's Ischemia Syndrome Evaluation (WISE) Study

Background:Limited brachial artery (BA) flow-mediated dilation during brachial artery reactivity testing (BART) has been linked to increased cardiovascular risk. We report on the phenomenon of BA constriction (BAC) following hyperemia.Objectives:To determine whether BAC predicts adverse CV outcomes and/or mortality in the women's ischemic Syndrome Evaluation Study (WISE). Further, as a secondary objective we sought to determine the risk factors associated with BAC.Methods:We performed BART on 377 women with chest pain referred for coronary angiography and followed for a median of 9.5 years. Forearm ischemia was induced with 4 minutes occlusion by a cuff placed distal to the BA and inflated to 40mm Hg > systolic pressure. BAC was defined as >4.8% artery constriction following release of the cuff. The main outcome was major adverse events (MACE) including all-cause mortality, non-fatal MI, non-fatal stroke, or hospitalization for heart failure.Results:BA diameter change ranged from -20.6% to +44.9%, and 41 (11%) women experienced BAC. Obstructive CAD and traditional CAD risk factors were not predictive of BAC. Overall, 39% of women with BAC experienced MACE vs. 22% without BAC (p=0.004). In multivariate Cox proportional hazards regression, BAC was a significant independent predictor of MACE (p=0.018) when adjusting for obstructive CAD and traditional risk factors.Conclusions:BAC predicts almost double the risk for major adverse events compared to patients without BAC. This risk was not accounted for by CAD or traditional risk factors. The novel risk marker of BAC requires further investigation in women. © 2013 Sedlak et al

Transients at stop-consonant releases

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1994.Includes bibliographical references (leaves 157-158).by Noel Steven Massey.M.S

A high enthaply [i.e., enthalpy] test facility powered by a gaseous core reactor.

This thesis document was issued under the authority of another institution, not NPS. At the time it was written, a copy was added to the NPS Library collection for reasons not now known. It has been included in the digital archive for its historical value to NPS. Not believed to be a CIVINS (Civilian Institutions) title.The feasibility of utilizing a gaseous core nuclear reactor to provide high enthalpy, high pressure gas flow for simulating atmospheric re-entry conditions was inves­tigated. The test facility uses a mixture of nitrogen and uranium in a closed cycle with no attempt to contain the uranium fuel within the core. The primary purpose of the facility is to provide high enthalpy, high shear flows for testing re-entry materials and shapes. Investigated in this study were the effects of the nitrogen-uranium mixture on reactor criticality, nuclear contamination of the test model, protection of the reactor core and nozzle structure from imposed heat loads and operating limitations of the test facility."Acknowledgement is made to the Department of the Navy, and to the United States Postgraduate School, Monterey, California, who made this work possible."http://www.archive.org/details/highenthaplyieen00flynLieutenant, United States Nav

Reliability Assessment of Graphite Specimens under Multiaxial Stresses

An investigation was conducted to predict the failure strength response of IG-100 nuclear grade graphite exposed to multiaxial stresses. As part of this effort, a review of failure criteria accounting for the stochastic strength response is provided. The experimental work was performed in the early 1990s at the Oak Ridge National Laboratory (ORNL) on hollow graphite tubes under the action of axial tensile loading and internal pressurization. As part of the investigation, finite-element analysis (FEA) was performed and compared with results of FEA from the original ORNL report. The new analysis generally compared well with the original analysis, although some discrepancies in the location of peak stresses was noted. The Ceramics Analysis and Reliability Evaluation of Structures Life prediction code (CARES/Life) was used with the FEA results to predict the quadrants I (tensile-tensile) and quadrant IV (compression-tension) strength response of the graphite tubes for the principle of independent action (PIA), the Weibull normal stress averaging (NSA), and the Batdorf multiaxial failure theories. The CARES/Life reliability analysis showed that all three failure theories gave similar results in quadrant I but that in quadrant IV, the PIA and Weibull normal stress-averaging theories were not conservative, whereas the Batdorf theory was able to correlate well with experimental results. The conclusion of the study was that the Batdorf theory should generally be used to predict the reliability response of graphite and brittle materials in multiaxial loading situations