3,983 research outputs found

    Real-time dynamic articulations in the 2-D waveguide mesh vocal tract model

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    Time domain articulatory vocal tract modeling in one-dimensional (1-D) is well established. Previous studies into two-dimensional (2-D) simulation of wave propagation in the vocal tract have shown it to present accurate static vowel synthesis. However, little has been done to demonstrate how such a model might accommodate the dynamic tract shape changes necessary in modeling speech. Two methods of applying the area function to the 2-D digital waveguide mesh vocal tract model are presented here. First, a method based on mapping the cross-sectional area onto the number of waveguides across the mesh, termed a widthwise mapping approach is detailed. Discontinuity problems associated with the dynamic manipulation of the model are highlighted. Second, a new method is examined that uses a static-shaped rectangular mesh with the area function translated into an impedance map which is then applied to each waveguide. Two approaches for constructing such a map are demonstrated; one using a linear impedance increase to model a constriction to the tract and another using a raised cosine function. Recommendations are made towards the use of the cosine method as it allows for a wider central propagational channel. It is also shown that this impedance mapping approach allows for stable dynamic shape changes and also permits a reduction in sampling frequency leading to real-time interaction with the model

    Suppression of Subsynchronous Vibration in the SSME HPFTP

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    Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP) hot-fire dynamic data evaluation and rotordynamic analysis both confirm that two of the most significant turbopump attributes in determining susceptibility to subsynchronous vibration are impeller interstage seal configuration and rotor sideload resulting from turbine turnaround duct configuration and hot gas manifold. Recent hot-fire testing has provided promising indications that the incorporation of roughened damping seals at the impeller interstages may further increase the stability margin of this machine. A summary of the analysis which led to the conclusion that roughened seals would enhance the stability margin is presented along with a correlation of the analysis with recent test data

    Equitability revisited: why the “equitable threat score” is not equitable

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    In the forecasting of binary events, verification measures that are “equitable” were defined by Gandin and Murphy to satisfy two requirements: 1) they award all random forecasting systems, including those that always issue the same forecast, the same expected score (typically zero), and 2) they are expressible as the linear weighted sum of the elements of the contingency table, where the weights are independent of the entries in the table, apart from the base rate. The authors demonstrate that the widely used “equitable threat score” (ETS), as well as numerous others, satisfies neither of these requirements and only satisfies the first requirement in the limit of an infinite sample size. Such measures are referred to as “asymptotically equitable.” In the case of ETS, the expected score of a random forecasting system is always positive and only falls below 0.01 when the number of samples is greater than around 30. Two other asymptotically equitable measures are the odds ratio skill score and the symmetric extreme dependency score, which are more strongly inequitable than ETS, particularly for rare events; for example, when the base rate is 2% and the sample size is 1000, random but unbiased forecasting systems yield an expected score of around −0.5, reducing in magnitude to −0.01 or smaller only for sample sizes exceeding 25 000. This presents a problem since these nonlinear measures have other desirable properties, in particular being reliable indicators of skill for rare events (provided that the sample size is large enough). A potential way to reconcile these properties with equitability is to recognize that Gandin and Murphy’s two requirements are independent, and the second can be safely discarded without losing the key advantages of equitability that are embodied in the first. This enables inequitable and asymptotically equitable measures to be scaled to make them equitable, while retaining their nonlinearity and other properties such as being reliable indicators of skill for rare events. It also opens up the possibility of designing new equitable verification measures

    Kennesaw State University - Maintenance Optimization and Cost Analysis

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    The Department of Housing and Residence Life was looking for ways to improve the quality of their work while saving costs at the same time. The department allowed the team to look over their work orders where the team noticed over 50% of the work orders were related to room turnover. After this discovery, the team focused all efforts on room turnover and went over the process in detail with management. The team asked to see the standard operating procedure for room turnover and learned that most of the staff did not know they had one. The team wanted to investigate why the staff was not aware of the SOP, so the team met with the assistant director of housing facilities to discuss why the SOP was not in use. He expressed that the SOP was not specific enough to direct the technicians in what the department was looking for. This led the team to begin thinking about creating a new SOP. After some research, the team learned that reducing variability was a good way of saving costs and that standard operating procedures were a reliable way of reducing variability. The team spoke with the department and reached the decision that a new SOP was the right decision for the department. The team began by shadowing the technicians to learn how the procedure should be done and where improvements could be made. As the team shadowed, they learned that resident assistants were supposed to be performing the inspections. This inspired the team to continue with creating the SOP but to also fully shift inspection duties to the resident assistants. After discussions with the housing department management, the new SOP created by the team was accepted and the trial runs with resident directors performing the inspections began. The team recommended that the department make the new SOP available to all resident and student assistants to ensure that each inspection was done in the same manner to reduce variability and rework

    Welfare Effect of Closing Loopholes in the Dividend-Withholding Tax: The Case of Cum-cum and Cum-ex Transactions

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    We study the effect of reforms that close loopholes in the enforcement of the dividend withholding tax (DWT). We focus on a Danish reform enacted in 2016, and compare Denmark to its Nordic neighbors. Our main outcome of interest is the quantity of stocks on loan. Before the reform all Nordic countries have a strong spike in stocks on loan centered around the ex-dividend day. The magnitude is large: on average excess stocks on loan peak at around 4 percent of the public float. The spike in lending is consistent with the most popular DWT arbitrage schemes. After the reform the spikes in Denmark disappear, but they continue in the other Nordics. We interpret this as evidence that the reform was successful at eliminating DWT arbitrage. We consider the welfare effects of the reform. Using synthetic difference-in-difference we find that stricter DWT enforcement resulted in a 130 percent (approx. 1.3 bln USD annually) increase in DWT revenue in Denmark. We detect no changes in foreign portfolio investment or dividend policy. We also consider DWT arbitrage among 15 European countries between 2010-2019. We find evidence of DWT arbitrage in all countries that levy DWT, though there is strong heterogeneity across countries. Importantly, similar to Denmark, Germany’s 2016 reform has eliminated the spikes in lending completely. We validate our identification strategy by showing that we find no evidence of DWT arbitrage in the UK, which does not levy a DWT

    Transient Response of Rotor on Rolling-Element Bearings with Clearance

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    Internal clearance in rolling element bearings is usually present to allow for radial and axial growth of the rotor-bearing system and to accommodate bearing fit-up. The presence of this clearance also introduces a “dead band” into the load-deflection behavior of the bearing. Previous studies demonstrated that the presence of dead band clearance might have a significant effect on synchronous rotor response. In this work, the authors investigate transient response of a rotor supported on rolling element bearings with internal clearance. In addition, the stiffness of the bearings varies nonlinearly with bearing deflection and with speed. Bearing properties were accurately calculated with a state of the art rolling bearing analysis code. The subsequent rotordynamics analysis shows that for rapid acceleration rates the maximum response amplitude may be less than predicted by steady-state analysis. The presence of clearance may shift the critical speed location to lower speed values. The rotor vibration response exhibits subharmonic components which are more prominent with bearing clearance

    Transient Response of Rotor on Rolling-Element Bearings with Clearance

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    Internal clearance in rolling element bearings is usually present to allow for radial and axial growth of the rotor-bearing system and to accommodate bearing fit-up. The presence of this clearance also introduces a “dead band” into the load-deflection behavior of the bearing. Previous studies demonstrated that the presence of dead band clearance might have a significant effect on synchronous rotor response. In this work, the authors investigate transient response of a rotor supported on rolling element bearings with internal clearance. In addition, the stiffness of the bearings varies nonlinearly with bearing deflection and with speed. Bearing properties were accurately calculated with a state of the art rolling bearing analysis code. The subsequent rotordynamics analysis shows that for rapid acceleration rates the maximum response amplitude may be less than predicted by steady-state analysis. The presence of clearance may shift the critical speed location to lower speed values. The rotor vibration response exhibits subharmonic components which are more prominent with bearing clearance

    The Spectral Energy Distribution of Dust Emission in the Edge-on spiral galaxy NGC 4631 as seen with Spitzer and the James Clerk Maxwell telescope

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    We explore variations in dust emission within the edge-on Sd spiral galaxy NGC 4631 using 3.6-160 μm Spitzer Space Telescope data and 450-850 μm JCMT data with the goals of understanding the relation between PAHs and dust emission, studying the variations in the colors of the dust emission, and searching for possible excess submillimeter emission compared to what is expected from dust models extrapolated from far-infrared wavelengths. The 8 μm PAH emission correlates best with 24 μm hot dust emission on 1.7 kpc scales, but the relation breaks down on 650 pc scales, possibly because of differences in the mean free paths between photons that excite the PAHs and photons that heat the dust and possibly because the PAHs are destroyed by the hard radiation fields within some star formation regions. The ratio of 8 μm PAH emission to 160 μm cool dust emission appears to vary as a function of radius. The 70 μm/160 μm and 160 μm/450 μm flux density ratios are remarkably constant even though the surface brightnesses vary by factors of 25, which suggests that the emission is from dust heated by a nearly uniform radiation field. Globally, we find an excess of 850-1230 μm emission relative to what would be predicted by dust models. The 850 μm excess is highest in regions with low 160 μm surface brightnesses, although the magnitude depends on the model fit to the data. We rule out variable emissivity functions or ~4 K dust as the possible origins of this 850 μm emission, but we do discuss the other possible mechanisms that could produce the emission
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