نشریه کارافن
سال هفدهم شماره 47 (بهار 1399)

The UPFC in Power Systems controls the line parameters and the power flow of the lines. On the other hand, controlling the power flow and lines parameters in transmission lines, maximizes the capacity of power transmission lines, increases network reliability, reduces line losses, increases power system efficiency, reduces energy loss and consumption management. Therefore, presenting a simple model of UPFC in power systems analysis is of interest to experts. In this paper, a simple model of upfc in steady state is presented. In the proposed model, the converter of upfc series is modeled with circuit elements. The proposed model will be included in the load distribution program without changing the dimensions of the Jacobine network matrix. To demonstrate the efficiency of the proposed model, the standard 14 bus are simulated

In some locations, using cell phone causes interference in performance of some electronic systems. Further, certain locations require silence and information security. Cell phone blocker or jammer is a device to interrupt the connections in the mobile phone. The signal emitted by the jammer resembles the mobile signal. As a pre-requisite condition jammer should have more power than the BTS transmitter in the desired range. Under this condition, mobile signal will be zero. The purpose of this paper is to design, simulate, and fabricate mobile blocker in GSM frequency bands. The proposed device is a strong transmitter capable of producing and emitting an interference signal in the P-GSM-900, DCS-1800, and PCS-1900 bands. This signal looks like noise and interrupts the connection of cell phones within a 10 m radius of the jammer. The capability to function in various GSM bands and reduce the cost of construction are the benefits of this plan.

This article analyzes the performance comparison of scheduling algorithms WFQ, PQ and FIFO using simulation of various scenarios such as (traffic crashes, incoming traffic, end-to-end delays, etc.) is covered in a wire network under VoIP. The active MSRP method has been suggested as a bandwidth reservation method. In this research, different queuing methods are evaluated with the help of OPNET simulator to manage, adjust and prioritize the packages in the buffers before sending them. Various parameters such as vibration, package’s delay changes, package’s end-to-end delay changes, and traffic of sent and received packages have been investigated. Also, the performance of different queuing designs is affected by different numbers of nodes. Finally, the best queuing scheme has been selected from this analysis and evaluation.

In this paper, a controller has been presented by the root locus method based on the state space average model of the Buck-Boost switching regulator with all of the converter’s parameters and uncertainties. In this model, the load current is unknown and the inductor, capacitor, diode and active switch are non ideal and have an on-state resistance. Furthermore, an on-state voltage drop has been considered for diode and active switch. The simple model of the system with two inputs and one output has been specified by neglecting the load current and assuming the ideal elements and a controller has been designed based on this model and roots locus method. The values of controller parameters have been calculated by the complete state space average model.

In this study, we try to control the temperature of a building consisting of four rooms with large time delays. In design process we use Krasovskii- Lyapunov method to guaranteed the stability of time delayed system. Because of difficulty of state estimation, an output feedback controller design method is used. for this purpose, we use linear Matrix Inequalities (LMI) and to solve LMIs, Matlab yalmip toolbox is utilized. Simulation results show that, by using our designed controller, even in presence of delay, uncertainty and disturbance, our system is stable and has proper performance.

In the present study, the thermal behavior of fluid in a square enclosure with two semi-circular constantis investigated numerically. The governing equations are solved by FlexPDE software, which is a simulation software base on the finite element method. The results showed that the distance between the two heaters will be a parameter affecting heat transfer; By reducing this distance, the natural convection heat transfer that is limited to the central part of the channel, is in the form of a symmetrical vertical column. Increasing the Hartmann number will lead to an increase in Lorentz force, a decrease in buoyancy force and consequently a decrease in temperature, a symmetrical temperature distribution and a predominance of conductive heat transfer. Increasing the Riley number increases the natural convection heat transfer in the form of free displacement, and by increasing the Riley number, the free-moving heat transfer will completely dominate the chamber.

These days overhead crane is widely used in different industries such as automobile, navigation and also transportation of tools in storerooms. In this paper, a new adaptive strategy of Kalman Filter based on Fuzzy logic in which it tunes the process noise covariance matrix Q is presented. The method proposed attempts to offset some of the assumptions made in UHF formulation and is also robust with respect to the nonlinearities in the dynamic system subjected to non-stationary noises. The matrix Q influences the Kalman gain matrix K and thus, tuning the covariance matrix in-turn amounts to tuning K, thereby improving the filter’s performance. Also this paper considers an important application the state estimation of a Crane, which dynamics are highly nonlinear and the noises affecting it are non-stationary.

Friction stir welding is one of the new methods of solid state welding. This welding method has many advantages over traditional methods of fusion welding due to low input temperature and non-melting and freezing of materials. In this study, the tensile strength variations of the welded specimens were investigated based on two parameters of the geometry of the tool and the angle of the device for the welding of polypropylene sheets. In order to obtain the optimal value of these parameters, other variables such as rotational speed and linear velocity of tools are assumed constant. After welding the samples, a standard tensile test was performed on the samples. The results show that the tool geometry has a great influence on the tensile strength and the appearance of the weld and the pieces welded by the tools with a welder's helmet have a higher strength. Also under the same conditions, the highest tensile strength is when the angle of the machine is 2°.

The present paper deals with experimental and numerical investigation of the mechanical properties of a piece produced by a dynamic powder compaction process under high-rate impact loading. Experimental tests are performed on metal powders made of aluminum by a gas launcher system. To validate the results obtained from the presented mathematical functions, we compare the results of the neural network model and the experimental data. In examining the error of experimental data and prediction based on the squared mean of the errors and the coefficient of determination show that the results obtained from the mathematical functions provide mathematical models for the final properties of the segment under optimal impact loading.

Determining the geomechanical parameters of rock mass is of particular importance in the design of industrial projects such as dams and tunnels. One of the most useful methods for determining these parameters is Hoek-Brown failure criterion. Because, rock mass quality is considered in this criterion on the basis of Geological Strength Index (GSI). Various methods were developed for determining GSI, and the results of each method differ from the results of the others. So far, the effect of these differences on the geomechanical parameters was not studied. The purpose of this research is to investigate the effects of GSI on the geomechanical parameters. Hence, different methods are reviewed and investigated at first. Latter, with the collected data (field study), this index is predicted and the effects of index variations on Hook-Brown constant parameters, strength parameters and deformation modulus with the proposed relationships are investigated. Results show that the difference in methods has a significant effect on geomechanical parameters. So that, a difference of 9 units in the geological strength index leads to more than 7GPa difference in the modulus of deformation.