نتایج جستجو برای: attenuation factor

تعداد نتایج: 886483  

2006
I. V. PROKHOROV

In this work, an inverse problem for the time-independent vector transfer equation for polarized radiation in isotropic medium is examined. In the problem, it is required to find the attenuation factor from known solution of the equation at the medium boundary. A formula is derived that relates the Radon transform of the attenuation factor with the radiation-flux density at the boundary. The un...

Journal: :Proceedings of the National Academy of Sciences 2010

Abbas Takavar Davood Beiki, Mehdi Sohrabi Mohammad Eftekhari, Mohsen Saghari N Mostaghim

SPECT detects γ-rays from administered radiopharmaceutical within the patient body. γ-rays pass through different tissues before reaching detectors and are attenuated. Attenuation can cause artifacts; therefore different methods are used to minimize attenuation effects. In our study efficacy of Chang method was evaluated for attenuation purpose, using a custom made heart phantom. Due to d...

It has been proved that ultrasonic energy can considerably increase the amount of oil recovery in an immiscible displacement process. Although many studies have been performed on investigating the roles of ultrasonic waves, based on the best of our knowledge, little attention has been paid to evaluate wave attenuation parameter, which is an important parameter in the determination of the energy...

Journal: :The Journal of the Acoustical Society of America 2002
Michael L Oelze William D O'Brien

Estimations of scattering parameters, such as average scatterer diameter, from rf signals backscattered from random media (tissues) are made from the frequency dependence of the rf signal. The frequency dependence of the rf signal backscattered from the medium is seen in the normalized power spectrum. The normalized power spectrum is found by taking the squared magnitude of the Fourier transfor...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه تربیت معلم تهران 1381

‏‎the purpose of the present study was to investigate the latent pattern underlying reading ability . some 272 male and female participants. english majors at the ba level , participated in the study. two valid tests were used in this study, the reading test developed exclusively for the purpose of this project and academic reading section of ielts. to investigate the possible latent underlying...

ژورنال: فیزیک زمین و فضا 2015

In this research, we have used 102 strong motion recordings from 2012 Ahar-Varzaghan earthquakes (Mw=6.5 and Mw=6.3) to study the form of attenuation of shear wave Fourier amplitude spectra of those two events. The analysis is carried out in a broad-band frequency range from 0.1 to 20 Hz. A bilinear shape for geometrical spreading is assumed based on nonparametric regression of the data. The hi...

Journal: :iranian journal of nuclear medicine 2003
abbas takavar mohammad eftekhari davood beiki mohsen saghari n mostaghim

spect detects γ-rays from administered radiopharmaceutical within the patient body. γ-rays pass through different tissues before reaching detectors and are attenuated. attenuation can cause artifacts; therefore different methods are used to minimize attenuation effects. in our study efficacy of chang method was evaluated for attenuation purpose, using a custom made heart phantom. due to differe...

2009
Seong Hyun Kim Won Jae Lee Hyo K. Lim Cheol Keun Park

OBJECTIVE This study was designed to assess superparamagnetic iron oxide (SPIO)-enhanced MRI findings of well-differentiated hepatocellular carcinomas (HCCs) correlated with their multidetector-row CT (MDCT) findings. MATERIALS AND METHODS Seventy-two patients with 84 pathologically proven well-differentiated HCCs underwent triple-phase MDCT and SPIO-enhanced MRI at a magnetic field strength ...

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