نتایج جستجو برای: density and attenuation
تعداد نتایج: 16878946 فیلتر نتایج به سال:
S U M M A R Y Cross-correlation of ambient seismic noise recorded by two seismic stations may result in an estimate of the Green’s function between those two receivers. Several authors have recently attempted to measure attenuation based on these interferometric, receiver–receiver surface waves. By now, however, it is well established that the loss of coherence of the crosscorrelation as a func...
Introduction: Osteoporosis is a bone disease in which there is a reduction in the amount of bone mineral content leading to an increase in the risk of bone fractures. The affected individuals not only have to go through lots of pain and suffering but this disease also results in high economic costs to the society due to a large number of fractures. A timely and accurate diagnosis of this disea...
The objective of this study was to devise an algorithm that can accurately estimate the attenuation along the propagation path (i.e., the total attenuation) from backscattered echoes. It was shown that the downshift in the center frequency of the backscattered ultrasound echoes compared to echoes obtained in a water bath was calculated to have the form Deltaf=mf(o)+b after normalizing with resp...
introduction: the use of radioactive iodine (131i) has become an important adjunct to the treatment of thyroid cancer and hyperthyroidism. salivary gland has the ability to concentrate radioactive iodine under normal circumstances. salivary gland dysfunction and dry mouth are the common side effectsof high-dose radioiodine therapy. the purposeof this study was to determine the absorbed dose of...
A through-thickness ultrasonic transmission (UT) in oriented strandboard (OSB) was done to compare the performance of direct-contact (DC) and non-contact (NC) ultrasonic systems. The DC measurements produced a higher velocity than the NC system for a given board type, possibly due to transducer’s compression over liquid couplant in the DC method. The UT responses correlated nonlinearly to sampl...
the introduction of ex vivo lung perfusion (evlp) in the practice of lung transplantation has allowed the reconditioning of the marginal grafts and their conversion into transplantable grafts. in addition, evlp can provide a platform for the application of various preventive measures to decrease the incidence of post-transplant complications. while the toronto team targets the attenuation of th...
UNLABELLED MR-based attenuation correction is instrumental for integrated PET/MR imaging. It is generally achieved by segmenting MR images into a set of tissue classes with known attenuation properties (e.g., air, lung, bone, fat, soft tissue). Bone identification with MR imaging is, however, quite challenging, because of the low proton density and fast decay time of bone tissue. The clinical e...
Recently, it was shown that both mean lung density (MLD) and the relative lung area with an attenuation of <-950 HU (RA950) are related to severity of asthma in nonsmoking asthmatics. The aim of the present study was to examine whether reduced computed tomography (CT) lung density during exacerbation could change after treatment. A cross-sectional study was performed to compare CT lung density ...
Background: Polyethylene composites including boron can be used as an effective neutron shield. Our investigation focuses on manufacturing borated polyethylene nano-composite. The purpose of this study is to design a radiation shield for use in both neutron and gamma fields. Materials and Methods: Borated polyethylene shields containing 2%, and 5% weight percentage of Boron nano-particles w...
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