سعید صدیقی

Due to the growing desire of people to join and use social networks, communication and shar ing data in these networks has been considered by various sciences such as political science, psychology, sociology, economics, etc. Hence, researchers have begun to distinguish and extract relationships between individuals from the data contained in these networks, to create more accurate communities. However, there is still no effective method to identify and extract communities based on social media data. In this article, a method has been proposed for social network accurate clustering by using Imperial Competitive Evolutionary Algorithm (ICEA) and selecting the initial population based on the density-based clustering criterion. The proposed method has improved the result of modularity about 21.45% in average, compared to rival basic ICEA and extracted more densed communities.

Durability of cement based material due to its uses in the building industry, always has been recognized as one of the main components of sustainable development of infrastructure and urban buildings. One way to improve the durability of concrete, especially in corrosive environments is to use natural pozzolans. On the other hand, with increasing carbon dioxide gas production in cities, the effects of carbonation phenomenon on the durability properties of concrete have increased. In this research, the effect of carbonation phenomenon on the durability properties of mortars containing natural pozzolans is investigated. In sample making two natural pozzolans including Khash pumice and Jajroud trass as substitute for cement by 20% and three water/cement ratios of 0.485, 0.44 and 0.4 were used. In this study, compressive strength test was used as an indicator of mechanical properties as well as an indicator of hydration degree in specimens. In order to study of durability properties of mortars carbonation depth, water absorb capillary and electrical resistance of specimens were measured. According to results, use of natural pozzolans reduces the compressive strength of specimens and increase depth of carbonation in them. Also, electrical resistance increases in samples. The results of capillary absorb water test show that carbonation phenomenon decreases capillary absorption coefficient in some samples. Finally, it can be concluded that the trass samples showed better performance than the pumice at an early age, while the pumice improved with increasing age. It is expected that the pumice performance was better than the pumice with give over time

Most intelligent underwater vehicles and remote control marine vehicles are usually equipped with optical cameras for underwater photography. However, due to water properties and its impurity, the quality of the images taken by these imaging equipment is not desirable, enough. Because, water reduces the light and by increasing the deep of water, the further light will diminish, which will result in the absorption of colors by water. Hence, image processing operations are crucial for underwater images .In this paper, a new method has been proposed to improve the contrast and quality of underwater images. In the proposed method, the two methods of contrast stretching and histogram equalization have been employed. In the histogram equalization phase, new methods have been introduced for thresholding and histogram clipping. The proposed method has been applied on a benchmark images dataset and the results have been compared with the results of common methods. The analysis of the proposed method results, compared to the Sathya et al., which is the best method compares to other rival methods, shows 40.16% increase in the contrast of the images, in the best case

Underwater imagery is one of the research areas of interest for marine exploration, such as environmental assessment, mineral detection and underwater living organisms analysis. For this research, clear, high-quality images of underwater objects are necessary. Underwater images, however, have always had visual, opaque, or excessive glare due to the lack of uniform and low light, which in turn results in the loss of detail in underwater images. On the other hand, the greater the depth of water, the more intense the light will diminish, which will result in the absorption of a series of wavelength by the water. This paper reviews, categorizes and compares the methods for enhancing underwater images. The results of this research show that color correction methods show better performance among other methods.

Improved image contrast is one of the most important operations used in image processing and visual processing applications. Histogram equalization is one of the most powerful ways to increase the contrast and improve the quality of digital images. However, this method usually causes an excessive increase in contrast and a loss of part of the image details. Many problems have been resolved in the past two decades in order to overcome the many problems of histogram equalization. In this paper, we have reviewed, categorized and compared the methods proposed in the field of histogram equalization for twenty years.