abstractbackground: an electron beam generated x-ray spectrum consists of characteristic x-ray and continuous bermsstrahlung. the aim of this research is calculating and comparing x-ray spectra for different target filter of mammograms. materials and methods: monte carlo is a very powerful tool to simulate a series of different target-filter assembly in order to calculate the x-ray spectra. mcn...

Myocardial perfusion SPECT imaging with Tc99m-sestamibi is the most accurate non-invasive means of detecting coronary artery disease and assessing the severity of perfusion abnormalities in the patients with coronary stenosis. Though simple and straight forward the results produced by the technique is very much affected by the details being used. One of the main problems with the test, wh...

Background: In CT systems, the machine utilizes a bowtie filter to shape the X-ray beam and remove lower energy photons. The shape of this bowtie filter is complicated and its geometry is often not available in detail. These renders the CT dose index (CTDI) to have different values in measurement versus Monte Carlo simulation studies and other analytical calculations especially in dosimetry of ...

A face recognition method based on long Haar-like filters is proposed. This filter takes a vector form whose components consist of 1 and −1. Although the learning of the filter is basically by the principal component analysis (PCA), our approach lies in constructing a highpass filter with 1 and −1 as filter coefficients. This approach yields a combinatorial optimization problem. Since the probl...

soil water potential was determined for three soil samples (i.e. 0-30, 30-60 and 60-90 cm depth) by the filter paper method (hamblin, 1981) and also for four non-destructive soil samples (i.e. 0-30, 30-50, 50-75 and 75-90 cm horizon) using pressure plate method.  in filter paper method, the filter paper is placed in hydraulic contact with the soil until an equilibrium state is attained in which...

one of the common problems in reflective seismic records is the existence of coherent linear and random noises which cause covering of the most important parts of reflective signals; therefore, it is necessary to attenuate them by processing methods. several processing techniques have been devised for attenuation of coherent linear noises and linear radon or ?-? transform is a powerful techniqu...

Idempotent filters produce a root signal in a single filter pass, i.e., the filter output is invariant to further filterings with the same filter. In this paper median based idempotent filter structures are introduced. Two approaches to generate these filters are studied: weighted median filters and median filter cascades. Two subclasses of n-dimensional idempotent weighted median filters, call...

In this paper, we give a kind of Cauchy 1-completeness in probabilistic quasi-uniform spaces by using 1-filters. Utilizingthe relationships among probabilistic quasi-uniformities, classical quasi-uniformities and Hutton [0, 1]-quasi-uniformities,we show the relationships between their completeness. In fuzzy quasi-metric spaces, we establish the relationshipsbetween the completeness of induced p...