mehdi esna ashari

The occurrence of ice lenses and the subsequent melting of the ice causes a lot of damage to the beds consisting of fine sand soils every year. Volumetric changes of soil during freezing-thawing is a factor that reduces soil strength and increases deformations. In this study, several laboratory measurements are presented to investigate the effects of freeze-thaw cycles on the behavior of cylindrical sand-cement-fiber specimens. Fine-grained sand has been chosen to investigate the effects of freeze-thaw. At the same time, chemical stabilization methods of soil by mixing with cement with amounts of 2, 4, and 6% by weight of dry soil and mechanical reinforcement by adding 0, 0.5, and 1% by weight of recycled nylon fibers have been used. This study shows that the presence of fibers next to cement causes obvious changes in the stiffness, strength, and durability characteristics of the samples under the effect of freeze-thaw cycles. From the findings of this study, it can be concluded that in samples without fibers, distinct and wide cracks are observed. While, in samples armed with fibers, the cracks are smaller and distributed in a wider width. The results related to the behavior of the samples during loading showed that in the samples reinforced with fibers, failure occurred due to the pull-out of the fibers. In 7-day dry samples (without the freezing-thawing cycle effect), the compressive strength of the samples increases with the addition of fibers. In the 28-day samples, with an increase of only 0.5% of fibers with a length of 0.5cm, the unconfined compressive strength increased , and its decrease was observed after that. In all 7d and 28d dry samples, with the increase of fiber size from 0.5cm to 1 and 1.5cm, the compressive strength of the samples has a decreasing trend. Also, by adding the percentage of fibers from 0.5 to 1%, the trend of decreasing strength of the specimens can be seen.

Fog computing emerged to meet to the needs of modern IoT applications, such as low latency, high security, etc. To this end, it brings the network resources closer to the end user. The properties of fog computing, such as heterogeneity, distribution, and resource limitations, have challenged application deployment in this environment. Smart service placement means deploying services of the IoT applications on fog nodes in a way that their service quality requirements are met and fog resources are used effectively. This paper proposes an efficient application deployment method in fog computing using communities. In contrast to previous research, the proposed method uses more factors than topological features to distribute network capacity more evenly between communities. This results in efficient use of network resources and better fulfillment of application requirements. In addition, according to our argument, using multiple criteria to prioritize applications will lead to better deployment and more effective use of resources. For this purpose, we use the number of application requests besides the deadline factor for application prioritization. Extensive simulation results showed that the proposed method significantly outperforms the state-of-the-art methods in terms of meeting deadlines, decreasing delays, increasing resource utilization, and availability by about 17, 33, 7, and 11 percent, respectively.

Clayey soils usually have low bearing capacity, high compressibility, shrinkage and swell characteristics. Several methods have been adopted to improve the geotechnical properties of such soils. Soil stabilizing by chemical materials is one of the most common methods for treating fine grained soils. Lime has been used to improve some mechanical and plastic properties of fine grained soils since many years ego. In recent years some studies has been also carried out to investigate the influence of adding pozzolany materials on the geotechnical properties of lime – treated clayey soils. Geotechnical behavior of clayey soils depends on chemistry of pore fluid. When drinking water is used to provide the needed moisture of soil in the laboratory, it will be lead to incorrect interpretation in engineering properties of soil where specific water such as sea water is utilized. Therefore, if the undrinkable water has been used to provide soil moisture, it is necessary to examine the behavior characteristics of the materials by the same water. For example, presence of some sulphates in the soil stabilized with lime leads to problems such as reduction of strength and increase of swelling in clay. In this laboratory study, effect of sea water on strength of stabilized kaolinite has been investigated by conducting several unconfined compression tests. The specimens were prepared at fore percentage of lime and pozzolan (i. e. 0%, 1%, 3%, 5%) by weight of dry soil and distilled water and three saline water which were taken from Caspian Sea, Persian Gulf and Urmia Lake. for every combination, weight of each material was determined exactly based on the optimum moisture content and maximum dry density which is obtained from the standard proctor compaction test. Clay and lime and pozzolan were mixed in dry condition properly and then water was added gradually. Afterwards, the mixtures were kept in plastic bags for 24 hours. Weight of each specimen was determined in accordance with given specific volume and obtained maximum dry density from compaction test. This weight was divided into four portion and each portion was compacted in 20 mm layer in a PVC mold. The specimens were cured in a oven having a temperature about 35 C for 3, 7 and 14 days. After each curing time a extruder was used to remove the specimens from the molds with constant rate vertically to avoid bending and formation of tensile cracks. Then the specimens were immediately tested under strain controlled at constant loading rate of 1. 0 mm per minute, according to requirements of ASTM D 2166. For each combination, three specimens were examined to assure repeatability of results. The results of conducted experiments indicate that unconfined strength of samples without additives (lime and pozzolan) prepared by sea water are higher than specimens containing distilled water. For the samples containing Urmia lake water, the unconfined strength were higher than the other samples. Also, for the specimens in which additive has been used, the strength of the samples containing Caspian Sea and Persian Gulf water were more than that with distilled water and the strength of samples containing Urmia lake water was less because of differences in the concentration of salts existed in the water. Finally, the results show that water minerals are higher in Urmia lake water, Persian Gulf and Caspian Sea, respectively.