جستجوی مقالات مرتبط با کلیدواژه « تبدیل فوریه » در نشریات گروه « مکانیک »

Image fusion is known as a synergetic process for merging multispectral and panchromatic images contents. So far, various methods have been developed in which the usage of the frequency domain is one of them. The frequency-based image fusion techniques are performed using high and low pass filters. So, the determination of the sizes of these filters would be a challenge. In this paper, a weighted index is proposed to determine the sizes and shapes of the low and high filters in fusion of the panchromatic and multispectral images. In the proposed method, the weights of the spectral and spatial indicators are independently estimated for each image. So, the effects of the differentiation of the image contents and different range of the indicators are properly adjusted to reach the optimum filtering. The comparison of the best results obtained from the proposed method with the other well-known fusion methods, in the used datasets, was indicated an average improvement of 58% in RMSEs.

Measuring the vital signs of human body, such as oxygen saturation, blood pressure, and heart rate is the greatest and basic stage of the diagnosis of various diseases, especially cardiovascular diseases. Various methods have been developed to measure these signs. In general, these methods are divided into invasive and non-invasive categories. Due to less damages of non-invasive methods, more attention has been paid to them in recent decades. Using mobile phone is one of the most important non-invasive approaches because of being common and accessible among people. In this article, after studying Photoplethysmographic methods and expressing theories related to this method, imaging photoplethysmography (IPPG) is used to measure heart rate. Regarding two proposed algorithms based on furies transfer and peak detection, implementation of these algorithms was done, using a camera and LED of smart phone on 20 people. Next, the heart was calculated. Finally, a comparison was made between the two methods, the results of which show that peak detection method has less error than furies transfer method.

In this study, 2D Asymmetric heat transfer in multi-layer composite cylinder is investigated, analytically. The boundary conditions are the most linear general boundary conditions which can cover all the heat transfer mechanisms consists of convection, conduction and radiation. The fibers are wounded around the cylinder. The angle of fibers and composite materials can be changed layer by layer. The governing equation of orthotropic conduction has been extracted and temperature distribution series have been obtained using the separation of variables method. In order to find the unknown series’ coefficients, three independent set of equations have been constructed by applying the boundary conditions inside/outside of cylinder and temperature/heat flux continuity between the layers. These set of equations have been solved using the orthogonal function relations and Thomas algorithm to find the recursive relation for unknown coefficients. The effect of design parameter, fiber angle and layers’ materials, have been investigated via two functional examples.

In this study, an exact analytical solution for two-dimensional steady-state conductive heat transfer in cylindrical composite laminates made of graphite-epoxy is presented. These laminates are in cylindrical shape and fibers have been winded around the cylinder in each layer. First, the appropriate Fourier transformation has been obtained using Sturm-Liouville theorem. Coefficients of series are achieved by solving a set of equations related to the thermal boundary conditions at inside/outside of the cylinder and temperature/heat flux continuity at the boundaries located between the layers. The solution of this set of equations is calculated using Thomas algorithm. In this article, the effect of fibers’ angle on temperature distribution of composite laminate is investigated under general boundary conditions. Here, we show that the temperature distribution for any composite laminates is between temperature distribution for laminates with fiber angles equal to the θ = 0 andθ = 90.