داریوش حسینی

Tides continuously change the water level in seas, and due to the continuity and dominance of currents caused by tides in bays, straits and estuaries, it is necessary to investigate the phenomena related to sediment transport and scouring in the surroundings of the structures located in the above areas will be illuminated more than before. In this research, by numerical simulation of the flow field and sediment transport, the scouring phenomenon under the pipelines caused by bidirectional currents has been investigated, and according to the values ​​of movement threshold speed, depth and number of tidal cycles to reach equilibrium, the characteristics of the scouring profile has been drawn. The obtained results indicate an increase in the depth and surface of the scour pit caused by the tidal current due to the alternating changes in the flow direction compared to the scour caused by the unidirectional current, and the vortex shedding process affects the final shape of the scour profile.

The main objective of the present study was to explore the barriers to the development of agricultural businesses in the incubator of Razi University, Iran. The research was an applied study in terms of objective and an exploratory mixed method in terms of data collection methodology. The statistical population was composed of agricultural businesses and their personnel in the incubator of Razi University in the qualitative phase and of the agricultural experts in the quantitative phase, as well. The samples for both qualitative and quantitative phases were taken by purposive sampling method. Ten people were sampled for the qualitative phase, and three were sampled for the quantitative phase. In qualitative phase, data were collected by semi-structured interviews that were kept on until theoretical saturation. Then, the content of the interviews was analyzed to classify the data. In quantitative phase, a questionnaire was developed according to the results of the first phase and was administered to the experts. Data were analyzed by the Analytical Hierarchy process method using Expert Choice Software Package. The results revealed that in-incubator agricultural businesses are challenged with a lot of barriers to their development. They were classified in five main categories including knowledge-skill, structural-legal, business-production environment, support-facility limitations, and administrative-financial. Among these factors, support-facility limitations were ranked the first with relative importance (weight of 0.237).

In this paper, the local scour process around pipelines due to steady currents has been investigated from different points of view using the numerical and physical models. In order to calculate the maximum scour depth under the pipe, a mathematical model based on the two-dimensional Laplace equation has been developed and the scour process on the 2D x-z vertical plane has been simulated, with the finite volume method being used to discretize the governing equation. In the developed numerical model, an equivalent boundary calculated using the Newton-Raphson iteration method, has been used to determine the deformed bed profile due to scour resulting from the subjected forces on the sediment particles on sea bed. In the physical models, emphasis has been focused on the effects of different parameters such as pipe diameter, water depth, velocity of flow and the interaction of the parallel pipes on local scour process. Finally, the numerical model results have been compared with the results obtained from the physical model and the other experimental data.