KARAFAN
Year:2021 | Volume:18 | Issue:1|Papers Count:12

Increasing the electrical demand causes the expansion of distributed generation sources and the interconnection of power systems. In the integrated power system, stability is one of the vital issues. The instability of the power system may cause a blackout. Therefore, the analysis of stabilities and sensitivities should be considered in power system studies. In this paper, the sensitivity analysis and eigenvalue of the induction wind generator were investigated by using a proper nonlinear model. First, the dynamic equations of the wind turbine induction generator were presented. For this purpose, the induction generator was connected to an infinite bus through a short transmission line. Sensitivity analysis was performed by changing some important system parameters. In this study, by changing the inductance and resistance of the transmission line, the variations of the induction generator were analyzed separately. Then the ratio r to x of the transmission line was investigated. Finally, the eigenvalues were considered for analysis of the case study's stability. Differential equations of the case study were solved using the Rang-Kutta order-four method with MATLAB software.

In the present study, the heat transfer of unsteady fluid flow between two oscillation plates under the influence of a magnetic field was investigated. The bottom plate was considered fixed and the upper plate could move closer or farther down to the bottom plate. The fluid flow was considered Newtonian, incompressible, two-dimensional, laminar, and unsteady. The governing equations including continuity, momentum and energy were in the form of partial differential equations (PDE); hence, they were transformed into ordinary differential equations (ODE) using similarity transformation. As an innovative method, the ODE governing equations were solved using a semi-analytical method named the Collocation Method (CM). For validity, a numerical 4th order Runge-Kutta method was used. The results revealed that by increasing the magnetic parameter, the horizontal velocity component decreased while the dimensionless temperature and heat transfer rate increased. An increase in the compression parameter led to a reduction of horizontal velocity component, dimensionless temperature, and heat transfer rate. Moreover, when Prandtl and Ecker numbers increased, the dimensionless temperature and heat transfer rate on the walls also increased.

One of the newest fields of study in the field of structural and earthquake engineering is the achievement of structural systems that quickly return to their pre-earthquake state and service after an earthquake. One of the newest of these systems is the Linked Column Frame (LCF) system, which protects the vertical loadbearing system during earthquakes by having the replaceable link beam members as a fuse member. The relative low cost and easy repair process in these systems lead to the rapid return to occupancy after an earthquake. In this system, the replaceable link beams used initially provide the initial rigidity of the system and then exhibit soft nonlinear behavior and ductility with energy dissipation resulting from the yield. In this paper, the behavior of the linked column frame system for retrofitting of the RC frames in two structures of 5-and 10-storeys were investigated. Based on the results of the nonlinear static analysis of the two 5-and 10-storey reinforced concrete structures retrofitted with LCF system, the amount of bearing capacity and the energy dissipation capacity of the structure retrofitted increased by an average of 3. 1 times compared to the structures without retrofitting. The plastic hinges were first formed in steel frames (LC frames) and the RC structure remained in an elastic state. Furthermore, the maximum and minimum shear absorption of seismic force percentage of the LC frames were approximately 80% and 13% in the lower and upper storeys, respectively.

A non-recyclable material that enters the environment is used car tires. Research shows that used tires are made of materials that, due to their non-decomposition under normal conditions, cause pollution and damage to the environment. According to research, one method of removing these materials is to use rubber waste in concrete. Therefore, in this study, aggregate composites were replaced by waste rubber particles the compressive strength of concrete was estimated by artificial neural network using the input parameters water to cement ratio, superplasticizer additive and granulation weight composition. The results of this study were compared with other related research studies and confirmed the superiority and high accuracy of the artificial neural network obtained in this study. The a-20 engineering index of the neural network was determined to be one and the error of 99% of the data was less than 15%, indicating the appropriate approximation of the compressive strength of concrete containing waste rubber particles by the artificial neural network. In addition, the results of the sensitivity analysis using the Millen method indicated a 40% effect of the weight of the superplasticizer additive as a sensitive parameter in this type of concrete.

One of the major challenges for the oil and gas industry is to keep buried metal pipes safe from faulting. This article discusses a solution to keep buried pipes safe. Wave-shaped joints, by their local deformation, create a rotational joint in a limited area so that other parts of the pipe remain intact. Abacus software was used to model the behavior of buried pipes due to slip direction fault displacement. In order to confirm the validity of the results of the numerical model, the pipe performance due to large axial displacement was compared and validated with the experimental results. An examination of the numerical results indicated that the presence of a wave connection can lead to a very good performance of the pipe in eliminating the buckling area and reducing the amount of plastic strain by approximately 80%.

The use of polyurethane as a sacrificial coating is an important factor in reducing risks and improving the safety of structures against explosions caused by war and terrorist attacks. The parameters of polyurethane can have a positive effect on reducing damage to tunnels under the impact of surface explosions. In this paper, the effect of density and thickness of the protective cover of polyurethane (as an energy absorber) in reducing the damage caused by surface explosions on underground tunnels was studied by computer simulation with AUTODYN software. Six different foam modules with thicknesses between 60 and 150 cm, and five different types of foams with densities between 90 and 250 kg / m 3 and their ability to reduce the maximum pressure caused by an explosion were compared. The results of this study illustrated that by increasing the thickness of the protective cover of polyurethane, a significant decrease occurred in the amount of pressure and vertical displacement in the tunnel crown. Moreover, the findings on the effect of polyurethane density indicated that at a density of 140 kg/m3, the optimum reduction in pressure in the tunnel crown occurred.

Due to the important environmental effects on human life and the conflict between the mining process and environmental factors, the enactment of protectionist environmental laws in the mining industry has received extensive attention particularly in countries with high mineral potential. In this regard, this study developed a novel conceptual framework to identify the environmental protection laws in Iran by considering the mining environmental laws and regulations in different countries such as Australia, Chile, India, Turkey, Canada, South Africa, and China. This helps to apply the experiences of the abovementioned countries in resolving similar conflicts in Iran's mining industry. The environmental protection laws were selected based on their legislation background in the field of mining, participation in environmental treaties, success in the field of mining trade, and pioneering in the revision of mining laws. The proposed framework demonstrated that Iran’ s mining environmental laws require revision and more transparency to avoid ambiguity and conflict with mining property laws and governmental rights.

Sar-e-Chah-e-Shur area is located in the eastern part of Iran and is adjacent to Lut block. Due to subduction, this area of Iran has a high potential for the formation of various minerals, particularly copper ores. Remote sensing data can be used effectively for the mapping of altered zones related to copper deposits due to the extension of the zones and poor vegetation coverage in the area. Advanced Space-born Thermal and Emission Reflectance Radiometer (ASTER) sensor, by covering a relatively wide range of electromagnetic spectra and storing ground surface information in three visible and near infrared (VNIR) bands, six shortwave infrared (SWIR) bands and five thermal infrared (TIR) bands (a total of 14 bands), has created favorable conditions for detecting alteration zones. In this research, the data of this sensor was used to separate the algal, cercitic, propolitic and iron oxide alterations related to copper ores in the 1: 100000 map of Sar-e-Chah-e-Shur, located in the southwest of Birjand, Iran. In the present study, alteration zones associated with porphyry copper were identified using various processing methods including false color combination, band ratio, standard analysis and selective component. The results of the present study field processing and surveys demonstrated the expansion of alteration zones in the study area and the optimal accuracy of the ASTER sensor. In the 13 visited areas, the existence of the desired alterations was confirmed.

In this study, the effect of variable parameters of 3D printing on tensile, compressive and bending strengths and impact resistance of parts made of Polyoxymethylene by Fused Deposition Modeling (FDM) method was investigated. The appropriate solution for printing the first layer and the best level for each variable was provided to achieve the best print quality of parts. In addition, the effect of layer height, nozzle temperature, filling pattern and print filling angle on the mechanical properties (compressive and bending strengths and impact and compressive resistance) of the parts was investigated and the Taguchi method used to design experiments and determine the effects. According to the results of the experiments, the highest tensile and bending strengths were obtained in wiggle and rectilinear print patterns, respectively. For impact testing, the Wiggle Print pattern provided the maximum impact energy. Finally, for pressure testing, the best conditions were observed in the rectilinear pattern. In the impact test, the nozzle temperature and print pattern were the most effective parameters, while in the pressure test, the print pattern was the most effective parameter. In addition, the best print temperature was reported to be 260 ° C.

The subject of the present study is production scheduling taking into consideration the payment of penalties. The purpose of production scheduling is to allocate limited resources over time to perform a group of activities. Therefore, the aim of the research was to develop an appropriate schedule in a production system that deals with issues such as various interruptions in production, lack of forecasting of raw materials required and time required for production, inability to decide on the composition of production which will lead to damages caused by delay and work stoppage. If the work is completed after the delivery date, there will be a penalty for late payment due to customer dissatisfaction, a contractual penalty or loss of credit. Reliability engineering must ensure that components and subsystems meet the defined requirements over a period of time. The research design was based on solving standard sample problems. In this regard, this research provided a mathematical model for multiple purpose scheduling. The scheduling problem was solved in the form of a reliability problem. Findings showed that solving the problem of production scheduling in the form of reliability performed well in terms of finding optimal solutions. The reliability of the system was also confirmed in 14 sample problems.

The prediction of stocks on the stock market and how the symbols are changed are one of the most applied and popular researches. By predicting the symbols with the least error, a person can succeed in the stock market. In this paper, a new network including a neural-fuzzy sink function and an improved grasshopper optimization algorithm was used to predict the value of symbols. In this regard, to predict and model the stock symbols, black-box modeling and AR (Autoregressive) model were used. Model order was determined by using the gray wolf algorithm. To optimize the network’ s linear parameters, a hybrid algorithm comprising of least square algorithm for initialization, recursive least square for online training, and a grasshopper optimization algorithm was used to optimize nonlinear parameters. The simulation illustrated that by providing a new structure, the gray wolf algorithm can determine the order of the model and the terms with the most impact on the steel symbol, effectively. In addition, the proposed network and algorithm had less error than other methods such as neural networks for predicting stock value, and the grasshopper optimization algorithm converged with the adaptive learning rate more rapidly.

In this study, the removal of Zn (II) ions from wastewater using an agro-waste, green pea (Pisum sativum) pod as low-cost adsorbent material was investigated. Green pea pod (Pisum sativum) is as an organic solid waste material that has high adsorbing capacity in removal of heavy metal ions from wastewater and can be very effective in treating industrial aqueous solutions that are important sources of water and soil pollution. The removal studies were done as a function of pH, contact time, adsorbent amount and initial metal ion concentration in the batch system. With increasing pH of the solutions, the adsorption of zinc by green pea pods also increased and adsorption capacity attained a maximum value at pH=8. By increasing the contact time, the amount of zinc adsorbed increased and reached equilibrium after 60 min. However, by increasing the amount of adsorbent to the solution, the adsorption of zinc decreased. By increasing initial concentration of zinc ions, the percentages of adsorption decreased but the metal uptake increased. Langmuir and Freundlich adsorption isotherm models were applied to determine the efficiency of pea pods used as an adsorbent. The linear regression analysis showed that the experimental data perfectly fit both models.