BACKGROUND Exposure measurement error in copollutant epidemiologic models has the potential to introduce bias in relative risk (RR) estimates. A simulation study was conducted using empirical data to quantify the impact of correlated measurement errors in time-series analyses of air pollution and health. METHODS ZIP-code level estimates of exposure for six pollutants (CO, NOx, EC, PM2.5, SO4,...

This paper presents measurements of sound velocity and attenuation in olive oil, with known chemical composition, as a function of pressure, within the range of pressure up to 0.7 GPa. Dependencies of sound velocity, relative ultrasonic wave attenuation, volume, and adiabatic compressibility on pressure show discontinuities. This proves the existence of the first order phase transition in olive...

An analysis is made of the measured distributions of the fade slope of rain attenuation, conditional for attenuation values, measured at Eindhoven University of Technology from the satellite Olympus. It is found that the distribution is similar for positive and negative fade slopes and independent of frequency in the range from 12 to 30 GHz. A distribution model for the conditional distribution...

Knowledge of x-ray attenuation is essential for developing and evaluating x-ray imaging technologies. For instance, techniques to better characterize cysts at mammography screening would be highly desirable to reduce recalls, but the development is hampered by the lack of attenuation data for cysts. We have developed a method to measure x-ray attenuation of tissue samples using a prototype phot...

Traditional broadband transmission method for measuring acoustic dispersion and attenuation requires the measurement of the thickness of the specimen, the transmission coecient at the water±specimen interface, and the Fourier spectra of two transmitted pulses. A new method has recently been developed that can determine both the thickness and dispersion of the specimen by utilizing the phase sp...

Previous reports have shown that the variance in ultrasound attenuation measurements is reduced when spatial and frequency compounding were applied in data acquisition and analysis. This paper investigates factors affecting the efficiency of compound attenuation imaging methods. A theoretical expression is derived that predicts the correlation between attenuation versus frequency slope (beta) e...

Rain attenuation is an important aspect of signal propagation above 10GHz frequency. The attenuation time series generation from point rain rate measurement is crucial due to unavailability of actual signal measurements. In this paper, a simple and realistic approach has been demonstrated for better estimation of rain attenuation using Ku-band signal propagation data and ground rain rate measur...

Abstract In order to solve the problems of difficult measurement, inaccurate results and serious interference diffusion attenuation in nondestructive evaluation grain size magnesium alloy components with complex profile, sound field models plane, cylindrical conical parts based on multiple Gaussian beam method are studied, mechanism ultrasonic propagation medium curved test blocks analyzed, An ...

This article is motivated by a time-to-event analysis where the covariate of interest was measured at the wrong time. We show that the problem can be formulated as a special case of survival analysis with heterogeneous covariate measurement error and develop a general analytic framework. We study the asymptotic behavior of the naive partial likelihood estimates and analytically demonstrate that...

Although is not a major error source at C-band, attenuation may degrade the radar measurement to a considerable degree in situations like a precipitation event in the radar shadow of a strong convective cell, or may affect precipitation accumulation estimates at distances far from the radar site. For C-band radars, attenuation can be corrected using different methods depending on the type of me...