Browsing by Subject "validation"

Now showing 1 - 9 of 9

Almost All Of Kepler's Multiple-Planet Candidates Are Planets
(2012-05) Lissauer, Jack J.; Marcy, Geoffrey W.; Rowe, Jason F.; Bryson, Stephen T.; Adams, Elisabeth; Buchhave, Lars A.; Ciardi, David R.; Cochran, William D.; Fabrycky, D. C.; Ford, Eric B.; Fressin, Francois; Geary, John; Gilliland, Ronald L.; Holman, Matthew J.; Howell, Steve B.; Jenkins, Jon M.; Kinemuchi, Karen; Koch, David G.; Morehead, Robert C.; Ragozzine, Darin; Seader, Shawn E.; Tanenbaum, Peter G.; Torres, Guillermo; Twicken, Joseph D.; Cochran, William D.
We present a statistical analysis that demonstrates that the overwhelming majority of Kepler candidate multiple transiting systems (multis) indeed represent true, physically associated transiting planets. Binary stars provide the primary source of false positives among Kepler planet candidates, implying that false positives should be nearly randomly distributed among Kepler targets. In contrast, true transiting planets would appear clustered around a smaller number of Kepler targets if detectable planets tend to come in systems and/or if the orbital planes of planets encircling the same star are correlated. There are more than one hundred times as many Kepler planet candidates in multi-candidate systems as would be predicted from a random distribution of candidates, implying that the vast majority are true planets. Most of these multis are multiple-planet systems orbiting the Kepler target star, but there are likely cases where (1) the planetary system orbits a fainter star, and the planets are thus significantly larger than has been estimated, or (2) the planets orbit different stars within a binary/multiple star system. We use the low overall false-positive rate among Kepler multis, together with analysis of Kepler spacecraft and ground-based data, to validate the closely packed Kepler-33 planetary system, which orbits a star that has evolved somewhat off of the main sequence. Kepler-33 hosts five transiting planets, with periods ranging from 5.67 to 41 days.
Alternative Approach on an In-Situ Analysis of the Thermal Progression During the LPBF-M Process Using Welded Thermocouples Embedded into the Substrate Plate
(University of Texas at Austin, 2019) Schnell, N.; Siewert, M.; Kleszczynski, S.; Witt, G.; Ploshikhin, V.
Laser powder bed fusion (LPBF-M) is a very potent technology for creating highly individualized, complex, and functional metal parts. One of the major influencing factors is the thermal progression. It significantly determines size accuracy, microstructure and process stability. Therefore, creating an enhanced understanding of thermal phenomena through measurements and simulations is crucial to increase the reliability of the technology. Current research is mainly based on temperature measurements of the upper layer, leaving major scope for the conditions at the substrate-part-interface. This area is of utmost technical importance because it serves as the main heat sink. Insufficient heat dissipation leads to accumulations of heat, deformations, and process breakdowns. This contribution presents a simple and flexible method to analyze the thermal progression close to the part inside the substrate plate. The acquired data shows very high consistency. Additionally, the results are compared to a model created using an ISEMP developed FEM-Software which shows promising results for validation studies.
Letter to H.B. Stenzel from Gordon Gunter on 1951-07-24
(1951-07-24) Gunter, Gordon A.
Letter to H.B. Stenzel from Gordon Gunter on 1952-10-15
(1952-10-15) Gunter, Gordon A.
Letter to H.B. Stenzel from Gordon Gunter on 1952-10-20
(1952-10-20) Gunter, Gordon A.
Older And Younger Adult Cochlear Implant Users: Speech Recognition In Quiet And Noise, Quality Of Life, And Music Perception
(2015-03) Sladen, Douglas P.; Zappler, Amanda; Zappler, Amanda
Purpose: To determine whether older cochlear implant (CI) listeners differ from younger CI listeners on measures of speech understanding, music perception, and health-related quality of life (HRQoL). In the study, the authors hypothesized that speech recognition would be more difficult for older adults, especially in noisy conditions. Performance on music perception was expected to be lower for older implanted listeners. No differences between age groups were expected on HRQoL. Method: Twenty older (>60 years) and 20 younger (<60 years) implanted adults participated. Speech understanding was assessed using words and sentences presented in quiet, and sentences presented at +15, +10, and +5 dB signal-to-noise ratio conditions. Music perception was tested using the University of Washington Clinical Assessment of Music, and HRQoL was measured using the Njimegen CI survey. Results: Speech understanding was significantly lower for the older compared with the younger group in all conditions. Older implanted adults showed lower performance on music perception compared with younger implanted adults on 1 of 3 subtests. Older adults reported lower HRQoL benefit than younger adults on 3 of 6 subdomains. Conclusion: Data indicate that older CI listeners performed more poorly than younger CI listeners, although group differences appear to be task specific.
Review of AM Simulation Validation Techniques
(University of Texas at Austin, 2017) Flood, Aaron; Liou, Frank
Due to the complexity of Additive Manufacturing (AM), it can require many trial runs to obtain processing parameters which produce a quality build. Because of this trial and error process, the drive for simulations of AM has grown significantly. Simulations only become useful to researchers if it can be shown that they are true representations of the physical process being simulated. All simulations have different methods of validation to show that they are an accurate representations of the process. This paper explores the various methodologies for validation of laser based metal AM simulations, focusing mainly on the modeling of the thermal processes and other characteristics derived from thermal history. It will identify and explain the various validation techniques, specifically looking at the frequency of reported use of each technique.
Thermal Simulation and Experiment Validation of Cooldown Phase of Selective Laser Sintering (SLS)
(University of Texas at Austin, 2017) Ji, Yi; Taylor, Samantha; Fish, Scott; Beaman, Joseph
Thermal stresses, induced by inhomogeneous temperature distribution inside a part during the cooldown phase of selective laser sintering, can be a major cause of part rejection for geometric deviation from its as-built specification. A validated cooldown simulation can provide predictions of temperature distribution in both parts and part cake which may enable alternative cooling profiles to reduce the likelihood of such rejections. This work describes experiments and comparative simulations developed to validate a sample tool for developing cool down control profiles in an SLS machine. In the experiments, thermocouples were inserted inside the part cake to monitor temperature at preselected locations during cooldown. The results from initial experiments and simulations were compared at these locations, to obtain improved estimates of uncertain powder conductivity and convective heat transfer parameters. The resulting simulation was then compared with independent experiments to evaluate the accuracy of such simulations. Though diffusion time in the part cake prevents active closed loop control in cooldown based on thermal measurements at the part, the simulation can be used to determine an open loop control profile for the build box heaters based on temperature gradient and resultant stresses inside the part.
Transit Timing Observations From Kepler. II. Confirmation Of Two Multiplanet Systems Via A Non-Parametric Correlation Analysis
(2012-05) Ford, Eric B.; Fabrycky, Daniel C.; Steffen, Jason H.; Carter, Joshua A.; Fressin, Francois; Holman, Matthew J.; Lissauer, Jack J.; Moorhead, Althea V.; Morehead, Robert C.; Ragozzine, Darin; Rowe, Jason F.; Welsh, William F.; Allen, Christopher; Batalha, Natalie M.; Borucki, William J.; Bryson, Stephen T.; Buchhave, Lars A.; Burke, Christopher J.; Caldwell, Douglas A.; Charbonneau, David; Clarke, Bruce D.; Cochran, William D.; Desert, Jean-Michel; Endl, Michael; Everett, Mark E.; Fischer, Debra A.; Gautier, Thomas N, III; Gilliland, Ron L.; Jenkins, Jon M.; Haas, Michael R.; Horch, Elliott; Howell, Steve B.; Ibrahim, Khadeejah A; Isaacson, Howard; Koch, David G; Latham, David W; Li, Jie; Lucas, Philip; MacQueen, Phillip J; Marcy, Geoffrey W; McCauliff, Sean; Mullally, Fergal R; Quinn, Samuel N; Quintana, Elisa; Shporer, Avi; Still, Martin; Tenenbaum, Peter; Thompson, Susan E; Torres, Guillermo; Twicken, Joseph D; Wohler, Bill; Kepler Sci, Team; Cochran, William D.; Endl, Michael; MacQueen, Phillip J.
We present a new method for confirming transiting planets based on the combination of transit timing variations (TTVs) and dynamical stability. Correlated TTVs provide evidence that the pair of bodies is in the same physical system. Orbital stability provides upper limits for the masses of the transiting companions that are in the planetary regime. This paper describes a non-parametric technique for quantifying the statistical significance of TTVs based on the correlation of two TTV data sets. We apply this method to an analysis of the TTVs of two stars with multiple transiting planet candidates identified by Kepler. We confirm four transiting planets in two multiple-planet systems based on their TTVs and the constraints imposed by dynamical stability. An additional three candidates in these same systems are not confirmed as planets, but are likely to be validated as real planets once further observations and analyses are possible. If all were confirmed, these systems would be near 4:6:9 and 2:4:6:9 period commensurabilities. Our results demonstrate that TTVs provide a powerful tool for confirming transiting planets, including low-mass planets and planets around faint stars for which Doppler follow-up is not practical with existing facilities. Continued Kepler observations will dramatically improve the constraints on the planet masses and orbits and provide sensitivity for detecting additional non-transiting planets. If Kepler observations were extended to eight years, then a similar analysis could likely confirm systems with multiple closely spaced, small transiting planets in or near the habitable zone of solar-type stars.