In this study, the transient Dynamic analysis of grid-stiffened composite conical shells is discussed. The transient Dynamic response of the composite conical shell with simply supported boundary conditions under the lateral impact load, which is applied extensively and uniformly on a certain surface, is obtained using the convolution integral and based on the method of addition of modes. The validation of the obtained results has been done with the help of references and ABAQUS finite element software. The effects of various parameters such as fiber angle, geometric ratios, type, etc. have been investigated in forced vibrations. Finally, the effect of reinforcing the conical shell with the help of grid-stiffened structures has been studied.

In data grid, using reservation is accepted to provide scheduling and service quality.Users need to have an access to the stored data in geographical environment, which can be solved by using replication, and an action taken to reach certainty. As a result, users are directed toward the nearest version to access information. The most important point is to know in which sites and distributed system the produced versions are located. By selecting a suitable place for versions, the versions having performance, efficiency and lower access time are used. In this study, an efficient method is presented to select the best place for those versions created in data grid by using the users’ firefly algorithm which is compared with two algorithms. Results show that firefly algorithm has better performance than others.

The Dynamic erosion characteristics of pipe bends exposed to gas-solid two-phase flow are investigated by using an erosion-coupled Dynamic meshing method to elucidate the erosion failure phenomenon that is common in pipe elbows, transporting coal fly ash and subjected to particle erosion. The static mesh is compared with the erosion-coupled Dynamic mesh method by CFD. The Dynamic erosion characteristics of bends with different r/D ratios, D and r are investigated before and after surface deformation under gas-solid two-phase flow. The results lead to the following conclusions: Improved performance of the erosion-coupled Dynamic mesh by taking full consideration of the coupling between the erosion-induced surface deformation and the particle motion under prolonged erosion. The erosion rate at the elbow changes significantly upon surface deformation, and the sites with a high risk of erosion shift downstream. With increasing of deformation, the larger the r/D ratio, the more obvious the concentration of erosion location evolving downstream. As D decreases, the high-risk erosion areas become more concentrated. In particular, the emergence of the “bending increase” phenomenon leads to a different perception of how r/D ratio and the diameter affect erosion in static-grid simulations: a larger r/D ratio of the elbow makes it more sensitive to surface deformation and increases the erosion rate. This study leads us to consider the coupled deformation of erosion in the context of erosion problems, which has important implications for predicting the service life of overflow components.

Recently, several types of Distributed Generators (DGs) have been connected together to form a small power system called a micro grid (MG). MG usually operates in normal connecting mode and is connected to the main grid. If a fault occurs in the main grid, MG will transfer immediately to the islanding mode. This paper developed a complete model which can simulate, in detail, the Dynamic performance of the MG during and subsequent to islanding occurrence. The developed model is used to investigate the effect of using storage batteries for enhancing MG Dynamic performance during all modes. Two cases are studied, the first case discusses the effect of the islanding process on the frequency, voltages and active powers of all micro sources when there are no storage batteries installed inside the MG. The second studied case investigates the effect of islanding occurrence on the MG performance when MG is equipped with two storage batteries. In the two studied cases, wind speed and irradiance vary continuously. Results proved that the existence of storage batteries led to dramatic improvement in the Dynamic performance of the MG during subsequent islanding occurrence. Also, MG performance, when exposed to a severe disturbance, led to an unacceptable frequency drop is studied and load shedding strategy activation during this situation is also highlighted.

In this paper, the experimental behavior of grid cylindrical composite structures which are used widely in engineering structures under ballistic impact is investigated. In the present study, the grid cylindrical composite samples were manufactured by the filament winding process with fiber placement procedure and perforated by projectile using the ballistic gas gun. Input and output velocities of projectile were recorded. The results show that presence of discrete ribs prevents spread damage from one cell to its adjacent cells and structure behaves differently against projectile with velocity near ballistic limit velocity and higher velocities. With approach to the ribs location ballistic limit has been increased. However due to reduce fracture area, overall and local deformations after impact in velocity which is higher than ballistic limit velocity, projectile has been come out from grid samples with higher velocity than simple composite shells. In this paper, delamination in outer composite shell and ribs, debonding between shell and ribs, residual velocity of projectile, fracture area of the grid specimens and the effects of curvature in two deferent velocities were reported and commented upon as results.

A voltage source inverter (VSI) is widely used as an interface for distributed generation (DG) systems. However, high-power applications with increasing voltage levels require an extra power converter to reduce costs and complications. Thus, a current source inverter (CSI) is used. This study presents a precise phasor modeling and control details for a VSI-based system for DG and compares it with a CSI-based system. First, the Dynamic characteristics of the system based on amplitude-phase transformation are investigated via small signal analysis in the synchronous reference frame. Moreover, the performance of the grid-connected system is determined by adopting the closed-loop control method based on the obtained Dynamic model. The control strategies employ an outer active-power loop cascaded with an inner reactive-power loop, which the inner loop is a single-input singleoutput system without coupling terms. The sensitivity analysis of the linearized model indicates the Dynamic features of the system. The simulation results for the different conditions confirm proposed model and design of the controller.

Power system deregulation and shortage of transmission capacities have led to increase interest in distribution generation (DG) sources. Several types of DGs are connected together and form a small power system called Micro-grid (MG). MG usually operates in normal connecting mode and is connected to the primary distribution network. When fault occurs in the primary distribution network, MG will transfer to islanding mode. This paper developed a complete model which can simulate the Dynamic performance of the MG during and subsequent to islanding process. The developed model contains one Solid Oxide Fuel Cell (SOFC), one single shaft micro turbine (SSMT), one flywheel, two photovoltaic panels and one wind generation system. All those micro sources coupled to the MG through inverter except the wind generation system. The developed model is used to investigate the effect of wind speed fluctuation, solar irradiance variation and failure of any micro source on the Dynamic performance of the MG. This case is compared with the original case which the wind speed and irradiance are assumed constant and all micro sources have no problems during the simulation interval. Results indicated that due to wind speed fluctuations and solar irradiance variations, there is a fluctuation on the MG frequency. Small voltage flicker is observed due to the change of the reactive power absorbed by the induction generator connected to the wind turbine. The third studied case, also, shows the effect of wind speed fluctuations and irradiance variation on the Dynamic performance of the MG when the MG is equipped with two storage batteries. Third case results indicated that using of storage batteries inside the MG can solve most of the problem which may be occur subsequent to islanding occurrence and enhance the overall performance of the MG. The developed model was built in Matlab, Simulink, environment.

In this article sub-grid modeling of Smagorinsky and Localized Smagorinsky Models are investigated. In modeling sub-grid scales, it is necessary to determine the Smagorinsky coefficient which is an experimental constant. Dynamic Models are developed to estimate this value more efficiently. In this research, the test filter is Gaussian, numerical method is based on the finite volume scheme, and a SIMPLE algorithm is used to evaluate the pressure. To perform computations on a personal computer, value of Reynolds number had chosen enough low to make a two dimensional modeling and comparison with respective experimental results possible.Comparison of numerical results shows high accuracy of the localized Dynamic models. More numerical investigations reveal that although localized Dynamic models need more computing time, but the higher resolution of the method makes it possible to use a coarser grid and hence compensate the extra CPU time.