The doubly asymptotic approximation (DAA) is a canonical relationship for the interaction between surface normal velocity and pressure. Its validity for a slender hemicapped cylinder is examined by formulating a frequency domain version of DAA using the global basis functions employed in the wave-number-based formulation of the surface variational principle [K. Wu and J. H. Ginsberg, ASME J. Vib. Acoust. 120, 392-400 (1998)]. The wet surface impedance matrix, which relates the spectral representation of normal velocity to a corresponding representation of pressure, is obtained according to a second-order version of DAA and according to the surface variational principle. Comparison and interpretation of the results reveals that DAA fails to account for highlights associated with transition from supersonic to subsonic surface waves as the surface wavelength decreases with frequency held constant.
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http://dx.doi.org/10.1121/1.428471 | DOI Listing |
Stat Methods Med Res
January 2025
Section of Biostatistics, Institute of Public Health, University of Copenhagen, Copenhagen, Denmark.
Recurrent events data are often encountered in biomedical settings, where individuals may also experience a terminal event such as death. A useful estimand to summarize such data is the marginal mean of the cumulative number of recurrent events up to a specific time horizon, allowing also for the possible presence of a terminal event. Recently, it was found that augmented estimators can estimate this quantity efficiently, providing improved inference.
View Article and Find Full Text PDFAcc Chem Res
January 2025
Department of Chemistry, Seoul National University, Seoul 151-747, South Korea.
ConspectusWhile traditional quantum chemical theories have long been central to research, they encounter limitations when applied to complex situations. Two of the most widely used quantum chemical approaches, Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT), perform well in cases with relatively weak electron correlation, such as the ground-state minima of closed-shell systems (Franck-Condon region). However, their applicability diminishes in more demanding scenarios.
View Article and Find Full Text PDFBiometrika
September 2024
Department of Mathematics, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093, USA.
In prevalent cohort studies with follow-up, the time-to-event outcome is subject to left truncation leading to selection bias. For estimation of the distribution of the time to event, conventional methods adjusting for left truncation tend to rely on the quasi-independence assumption that the truncation time and the event time are independent on the observed region. This assumption is violated when there is dependence between the truncation time and the event time, possibly induced by measured covariates.
View Article and Find Full Text PDFJ Appl Stat
May 2024
Division of Biostatistics and Bioinformatics, Herbert Wertheim School of Public Health and Human Longevity Science, University of California, San Diego, La Jolla, CA, USA.
The Mann-Whitney-Wilcoxon rank sum test (MWWRST) is a widely used method for comparing two treatment groups in randomized control trials, particularly when dealing with highly skewed data. However, when applied to observational study data, the MWWRST often yields invalid results for causal inference. To address this limitation, Wu (, Stat.
View Article and Find Full Text PDFBiom J
December 2024
Department of Biostatistics, School of Public Health, Virginia Commonwealth University, Richmond, Virginia, USA.
This paper introduces a novel approach to estimating censored quantile regression using inverse probability of censoring weighted (IPCW) methodology, specifically tailored for data sets featuring partially interval-censored data. Such data sets, often encountered in HIV/AIDS and cancer biomedical research, may include doubly censored (DC) and partly interval-censored (PIC) endpoints. DC responses involve either left-censoring or right-censoring alongside some exact failure time observations, while PIC responses are subject to interval-censoring.
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