a. rabiee

Due to the increasing occurrence of natural disasters, importance of maintaining sustainable energy for cities and society is felt more than ever. On the other hand, power loss reduction is a challenging issue of active distribution networks (ADNs). Therefore, the distribution network operators (DNOs) should have a certain view on these two problems in today’s smart grids. In this paper, a new convex optimization model is proposed with two objective functions including energy loss reduction in normal operating mode and system load shedding minimization in critical conditions after the occurrence of natural disasters. This purpose is fulfilled through optimal allocation of distributed generation (DG) units from both conventional and renewable types as well as energy storage systems (ESSs). In addition, a new formulation has been derived to form optimal micro-grids (MGs) aiming at energy loss reduction in normal operating condition and resiliency index improvement under emergency situations. The developed model is implemented in GAMS software and the studies have been tested and analyzed on the IEEE 33-bus system. The results verify the effectiveness of the proposed method in terms of energy loss reduction as well as resilience enhancement in extreme operation condition following severe disruptions in the system.

This paper discusses the implementation of an algorithm for solving 2D time-dependent neutron transport equations in heterogeneous media. A novel modular ray tracing algorithm where neutrons are allowed to travel a longer path before being removed from the structure, is adopted for the transient calculation. The time derivative of angular flux is considered as a major source of challenges in implementing the neutron transport equation, in which two cases for the time derivative of angular flux are included, first, the angular dependency of the time derivative is preserved and second mode, isotropic scalar flux approximation is applied to the time derivative. Sensitivity analysis on time step size has been investigated as an effective parameter on both computational accuracy and cost. Investigating the compatibility of the proposed numerical algorithm as well as considering the substantial role of delayed neutrons in transient processes, three multigroup mathematical models for delayed neutrons are evaluated along with the neutron transport equation. For the implementation of the verification algorithm, the well-known TWIGL benchmark is modeled and the results are compared with MPACT and DeCART codes.

The design and use of passive safety systems as one of the effective ways to increase reliability and safety level of nuclear power plants in new generation reactors has received much attention. In this paper, using RELAP5 computational code, the thermo-hydraulic analysis of the Passive Heat Removal System (PHRS) in the VVER-1000 reactor is investigated to ensure the capability of its performance under various conditions. For this purpose, the system nodalization is first extracted according to the available documentation and then the RELAP5 code input is developed. The results show that for 6.27 MPa pressure in steam generators and air temperature of 36 ° C, the system is able to remove 95.52 MW heat.

In this paper, quadratic convex relaxation (QCR) is used to relax AC optimal power flow (AC-OPF) used for reactive power scheduling (RPS) of the power system. The objective function is system active power loss minimization to optimally determine the tap position of tap-changers, the reactive power output of generating units, synchronous condensers, shunt capacitor banks, and reactors. The nonlinear and non-convex terms due to trigonometric functions cause the problem to be non-convex which results in trapping in local minimum or even not converging in large size power systems. Therefore, in this paper, the nonlinear terms and trigonometric function are relaxed by linear and quadratic functions. Furthermore, the product of two variables and multi-variables are relaxed by McCormick bilinear and multi-linear expressions, converting the AC-OPF of RPS to quadratic constraint programming (QCP) optimization problem. The proposed RPS method is studied based on IEEE RTS 24-bus test system. The results show the accuracy of the proposed (QCR) method to relax the AC-OPF optimization problem of RPS.

The risk assessment of local nuclear fuel melting in nuclear power plants (NPPs) due to its localized nature and the difficulty in accurate monitoring is of vital importance for safe operation of nuclear reactors. Experiences have shown that flow blockage accident without safety control rod axe man (SCRAM) can lead to local nuclear fuel melting which consequently affect the safety of NPPs. The purpose of this study is to analyze the transient states leading to local fuel melting based on ATWS-related events given in FSAR of the VVER-1000/V446 nuclear reactor including pump failure, local blockage, power level increasing and their combinations. In this work, a coupling framework is first developed based on the MCNPx and the COBRA/EN codes. After validation with available data, the results showed that despite 18% deviation from the mass flow rate reduction limitation, 470 kPa from the channel pressure drop limitation, and 204K from the clad temperature limitation in the most pessimistic situation, the reactor SCRAM does not occur. However, in these conditions (where SCRAM does not occur), 70% void fraction for 12 minitues is observed in some channels. Therefore, there may be dry spots and local melting of fuel in normal operational and ATWS conditions that need to be identified. According to the results, the occurrence of the void fraction above zero is locally expectant and an appropriate monitoring system should be used to identify weakness points of the system.

This paper presents a methodology for reactive power scheduling (RPS) of power system in the form of AC optimal power flow (AC-OPF) problem. The objective function is minimization of system total active power losses. The OPF optimally determines reactive power output of generating units and synchronous condensers, tap-changers ratio, shunt capacitor banks and reactors. The effect of tap-changer is modeled in the active and reactive power flow of transformer. The proposed method grantees secure operation of system in normal operating condition and also in contingency of transmission line outage. The validity of proposed method is studied based on IEEE RTS 24-bus. Results show the capability of suggested AC-OPF for RPS of system in base case as well as contingency of single line outage.

Electricity generation through renewable energy sources such as wind energy has been growing in recent years due to several reasons including free and infinite resources as well as their considerable impact on the reduction of fossil fuels consumptions as well as CO2 emissions. This paper aims to assess the impact of grid-connected large-scale wind farms in a region located in Iran, on the reduction of natural gas as well as gasoil fuel consumptions in heat-cycle power plants and their related CO2 emissions as a practical case study. The wind farms under study comprise about 51% of the total grid connected capacity of wind power generation in Iran by the end of March 2021. The total energy yielded by the studied wind farms are first extracted over a two-year period from April 2019 to March 2021 based on a detailed practical data and then, its impact is investigated on the reduction of natural gas and gasoil consumptions in a real heat-cycle power plant due to its practical fuel intake data. Finally, the reduction of CO2 emission is calculated as the result of reduction in the natural gas and gasoil consumptions of the considered heat-cycle power plant. The results of this practical case study well demonstrate the effective role of wind farms energy yields on the reduction of fossil fuels consumption in heat-cycle power plants and thus, the significant reduction of CO2 emission as one of the most crucial aspects of decarbonization and fossil fuel phase out plans.

Transmission lines switching and tap adjustment of power transformers are short-term alternatives to enhance the flexibility of power system operation. By a proper implementation of these alternatives, the operational problems such as lines congestion, bus voltage violations and excessive power losses can be alleviated. Traditionally, these two alternatives are applied separately due to the complexity of their simultaneous implementation as well as their coordination. In this paper, a DIgSILENT-based improved particle swarm optimization (IPSO) algorithm is proposed to implement the transmission switching and coordinated voltage control of power transformers, concurrently. The IPSO is implemented in DPL environment of Powerfactory-DIgSILENT, as a powerful software package commonly used by the electrical utilities. The proposed approach is applied to IEEE-14 bus system and the real transmission network of Zanjan Regional Electric Company (ZREC) located in Iran, in different scenarios considering all the existing practical constraints. The obtained results verify the effectiveness of the presented approach.

Using proper dimensionless coefficients that are insensitive to various operating conditions is a crucial issue during the utilization of a yawmeter probe. These dimensionless coefficients produce the deviation angle of flow, stagnation and static pressures. In the current study, these coefficients are analyzed using SPM analytical and experimental methods. A comparison of experimental and analytical results shows that SPM analytical method predicts the flow deviation coefficients satisfactorily at the operational angle range of three-hole probe. This method also calculates the stagnation pressure coefficient precisely at the deviation angle range of ±10 degrees. The experimental results show that due to the assumption of constant speed on the probe, the analytical method cannot calculate the static pressure accurately. Experimental observations also demonstrate that velocity is increased and pressure is decreased over the probe. This is due to the suction region at the downstream of probe. Unlike analytical results, experimental observations depict that at zero degrees, the flow static pressure is equal to the average of pressure at the left and the right side of probe. Due to sensitivity of dimensionless coefficients of flow static pressure to variation of Reynolds number, various values are reported at different kinds of literature for these coefficients. These coefficients change with Reynolds number variations and their accuracies are decreased. In the current study, a new proper dimensionless coefficient is introduced which represents minimum sensitivity to Reynolds number.

Flexible AC Transmission Systems (FACTS) devices have shown satisfactory performance in alleviating the problems of electrical transmission systems. Optimal FACTS allocation problem, which includes finding optimal type and location of these devices, have been widely studied by researchers for improving variety of power system technical parameters. In this paper, a DIgSILENT-based Discrete Particle Swarm Optimization (DPSO) algorithm is employed to manage the power flow, alleviate the congestion, and improve the voltage profile in a real case study. The DPSO have been programmed in DPL environment of DIgSILENT software and applied to the power grid of Gilan Regional Electric Company (GilREC), located in north of Iran. The conducted approach is a user-friendly decision making tool for the engineers of power networks as it is executed in DIgSILENT software which is widely used in electric companies for the power system studies. The simulation results demonstrate the effectiveness of the presented method in improving technical parameters of the test system through several case studies.

Critical heat flux has been recognized as the upper limit for the safe operation of many cooling systems which may lead to the occurrence of dryout causing a large temperature gradient in the heated wall. One way to increase the amount of the critical heat flux is to put in nanoparticles such as Al2O3 to the base fluid. The current research investigates the nanoparticles effect on dryout phenomenon using computational fluid dynamics. Boiling phenomena are simulated using the mechanistic model organized in Rensselaer Polytechnic Institute which is extended to analyze the critical heat flux by partitioning wall heat flux to liquid and vapor phases. It was shown that the dryout phenomenon can be delayed by increasing the nanoparticles concentration, and in certain concentration of nanoparticles (5 percent), dryout would not take place.

The necessity and importance of a high heat removal potential in various areas particularlyin nuclear applications are in a direct relationship with the excessively applied heat flux level. One wayto increase the heat transfer performance and subsequently enhance the threshold of the critical heatflux is to employ spacer grids accompanied by mixing vanes. In this study, the effect of the spacerswith mixing vanes on the critical heat flux characteristics in the dryout condition has been numericallyinvestigated employing the benefits of the Eulerian-Eulerian framework. In the current research, severalvane angles, including vane with 0, 15 and 25 degrees in comparison with the effect of the bare spacerwithout any mixing vanes on the flow characteristics were examined. It was shown that the existence ofthe spacer alone, delays the temperature jump under critical heat flux conditions. It was also concludedthat increasing the angle of the mixing vanes, further improves the heat transfer performance of thesystem by postponing the sudden temperature jump occurring in the channel; however, the presence ofthe spacers and vanes in the flow field imposes an increase of the pressure drop due to the constrictionon the coolant flow area.

One of the main goals of education is the development of skilled manpower . Due to the increasing population and demand for entering the universities and higher education institutions and also the economic problems, the issue of "entrepreneurs" is an important matter The  aim of  this paper is to evaluate the ability of entrepreneurial in Payame Noor university. It asked 450 students at this University in Tehran to answer the questionnaire with 0.86%  Cronbach's alpha coefficient and Likert respond method. The results show that: There is a significant and meaningful relation between student 's Creativity and independence and their willingness to entrepreneurship; Risk taking in male students is more than female students; Internal locus of control and independence in female students were significantly higher than male students; Achievement motivation, Internal locus of control and independence in basic science and engineering students were significantly more than the students in the humanities and Creativity in unemployed students was more than Employed ones. Internal locus of control and achievement motivation in Students who passed the Entrepreneurship  course was  more than Students who don' t passed it ;and Educational activities were related to the development of the components of creativity and motivation.

Providing a particular definition of crisis and introducing different classifications of different types of crisis, the present paper takes a structural approach to phenomenon of crisis. Hence, this study believes that all types of current crises of a society have capability to be projected into other crises and making a new crisis more huge than the sum of its constructing crises. With this approach, the author scrutinizes social, political, cultural and other aspects of today's society of Iran and analysis the connection between current crises of this society and issues such as development, globalization, new trends, and, structural changes in society. In the final sector, the author introduces his own analysis of crises of today's Iran and provides some suggestions for avoiding these crises or minimizing their effects.