In this paper, the idea of adaptive robust control (ARC) is integrated with a repetitive control algorithm to construct a performance oriented control law for a class of nonlinear systems in the presence of both repeatable and non-repeatable uncertain nonlinearities. All the uncertainties are assumed to be bounded by certain known bounding functions. The repetitive control algorithm is used to ...

BACKGROUND Effects of high iodine-concentration contrast material on the image quality of coronary CT angiography (CCTA) have not been well evaluated. PURPOSE To compare the image quality and attenuation values of CCTA between patients administered iopromide 370 and iomeprol 400 with the use of 64-slice multidetector CT. MATERIAL AND METHODS Patients were prospectively enrolled and were ran...

introduction: scattered photon is one of the main defects that degrade the quality and quantitative accuracy of nuclear medicine images. accurate estimation of scatter in projection data of spect is computationally extremely demanding for activity distribution in uniform and non-uniform dense media. methods: the objective of this paper is to develop and validate a scatter correction technique t...

introduction: acceptance test is a necessary procedure after spect system installation. the goal of this test is to reveal system's present condition, to compare it with manufacturer's specifications and also as a base for later tests. methods: this study investigated four spect systems in tehran. all of the quality control tests are performed on the basis of nema and iaea recommendations and b...

OBJECTIVE The aim of this study was to evaluate the potential of contrast media (CM) reduction in computed tomography angiography (CTA) of coronary artery bypass grafts (CABGs) when adapting CM volume to automatically selected tube voltages. MATERIAL AND METHODS Sixty consecutive patients (mean age, 71 ± 14.5 years) with a total of 176 CABGs (692 bypass segments) underwent contrast-enhanced p...

Tube current (mA) is one of the key technical scanning parameters for adjusting radiation dose in CT. To optimize radiation dose in CT, users can adjust mA either with manually selected mA values or with the application of automatic exposure control (AEC). The latter technique refers to automatic adaptation of mA on the basis of userspecified image quality and x-ray attenuation characteristics ...

in exploration seismology quality factor is widely used as a seismic attribute to identify anomalies related to attenuation, especially those caused by hydrocarbon. previous studies have indicated that seismic energy loss known as attenuation is greater for high frequency components of seismic data compared to the low frequency components. here the continuous wavelet transform is used to study ...

A of seismic waves is sensitive to the physical properties of the subsurface and has been observed in vertical seismic profiling (VSP) and reflection data. De et al. (1994) report measurements of the Pand S-wave quality factors from VSP surveys and sonic logs. Klimentos (1995) measures compressional and shear attenuation from sonic logs in sandstone formations with variable oil, water, and gas...