نشریه کارافن
سال هفدهم شماره 50 (زمستان 1399)

Computer networks are spreading widely and one of the most outstanding challenges in computer network security is detecting intrusions into networks. One of the main tools for detection is controlling network traffic and analyzing users’ behavior. One way of accomplishing this is to set classifications that specify the patterns in huge volumes of data. By means of data mining methods and introducing a binary label (normal pack, abnormal pack) and specifying the priority of data, abnormal data is detected leading to increased accuracy of network intrusion detection which in turn leads to improvement and maintenance of network security. In this paper, SVM algorithm is analyzed in terms of priorities and the effect of machine learning algorithm on accuracy of intrusion detection is investigated. The results show that using SVM is more advantageous compared to past approaches yielding better detection and increasing accuracy and right alarm detection.

Suppose R is a uniform commutative ring. The R-dependent intersection graph, represented by the symbol G (R), is a simple, directionless graph whose set of vertices is the set of all non-trivial ideals of R and two distinct vertices 𝐼, 𝐽 are joined if and only if 𝐼 ∩ 𝐽 ≠ (0). In this paper, the metric dimension of intersection graphs associated with commutative rings is examined and some metric dimension formulas for intersection graphs are provided. Suppose R is a uniform commutative ring. The R-dependent intersection graph, represented by the symbol G (R), is a simple, directionless graph whose set of vertices is the set of all non-trivial ideals of R and two distinct vertices  are joined if and only if  ‎. In this paper, the metric dimension of intersection graphs associated with commutative rings is examined and some metric dimension formulas for intersection graphs are provided.

Modeling and analysis of systems, particularly in complex systems with noise and uncertainty in behavior recognition and decision making of systems, is of vital importance. In this article, such system problems were solved to the greatest degree possible based on fuzzy theory. This fuzzy system has four input variables and two output variables. Since the fuzzy rules were obtained from an experienced expert in Electric Power Subsystem (EPS) design, the results were expected to be more practical and logical in comparison with the real behavior of the subsystem. The proposed fuzzy system can model the qualitative data of an expert. The simulated results had suitable accuracy in conceptual design compared with the practical data of remote sensing satellites. The results also showed that fuzzy systems can be used effectively to design the EPS of a remote sensing satellite.

One of the most important problems in control engineering is state estimation of a dynamical system based on measured data corrupted by noises. One of the most popular algorithms used for state estimation of a linear discrete time dynamical system is mixed Kalman/H-infinity filter. The performance of this filter is essentially depending on how exact statistics of noise characteristics are available. It is also not guaranteed that the process noise covariance matrix, and the measurement noise covariance matrix remain constant with time in a highly non-stationary noise condition. Thus, it is imperative to continuously tune the mixed Kalman/H-infinity accounting for the changing noise conditions in order to get good filter performance. This paper presents an algorithm of fuzzy based mixed Kalman/H-infinity filter for dynamically tuning the process noise and measurement noise covariance matrices. Fuzzy system in every step of the process using the difference between the actual position and speed of the balloon and the amount of observed data by the observer, an adaptive produce and this factor is used to update covariance matrix values. In this way, the Fuzzy Mixed Kalman/H-infinity filter can be more accurately estimated system state variables and therefore always mean square estimation error is minimized.

Over the previous few decades, bio-inspired (BI) organic process improvement techniques have experienced extraordinary popularity in the field of engineering. These techniques gift a troublesome competition to ancient numerical procedures that suffer from convexity and continuity assumptions and that usually use a gradient based mostly search that's sensitive to the initial resolution. Whereas initial BI techniques specially have been investigated by novel and improved variants. The population primarily based computing strategies are notably engaging for finding multi-objective (MO) problems due to their capability of producing an outsized variety of Pareto-optimal solutions in one run. In this paper, two algorithms of firefly and differential evolution concept is proposed as a performance metrics for switched reluctance motor (SRM) as control rod drive in small modular reactor. This work aims to prevail and amend the remarkable drawback of switched reluctance motor, which is torque ripple, by executed current control of the motor based on the PI controller in a closed-loop controller. Furthermore, the output power of the plant is optimized to trace the reference properly. The effectiveness and advantage of the system control scheme are presented in MATLAB software in real-time.

In this study, the thermal performance of a sample radiator under defined environmental conditions was studied. The relations governing the heat transfer for the air flow and the cooling fluid of water and ethylene glycol (50% -50%) were written in the radiator and then the characteristics of the radiator were changed and the relations re-examined. It was observed that the thermal performance of a radiator whose length was reduced by 25% but number of fins increased from 385 to 437 was equal to the thermal performance of the original radiator. The ϵ-NTU method was used to investigate this matter. Its optimal value was determined by the designed genetic algorithm 436. In addition, the distance between the two fins was reduced from 3.92 mm to 2.94 mm, the optimal value of which was determined by a genetic algorithm of 2.867 mm. Reducing the length of the radiator makes the radiator lighter and reduces construction costs, but reducing it too much can cause the cooling fans to come closer together and create a problem with heat dissipation.

Antioxidants One of the methods to increase the combustion efficiency in an internal combustion engine is to create swirl flow. In EF7 engine, there are two inlet valves per cylinder so small amount of swirl flow may be created. Most of the conventional methods for generating vortex current, even used in new engines, require major design and modifications of cylinder head, and their costs are significant. In this study, a new low-cost method was developed to create vortex flow. The goal of the changes is to develop inlet flow difference between the two inlet valves led to develop swirl flow in the cylinder in order to increase the combustion efficiency provided that the flow coefficient doesn’t face a loss. First, the swirl flow in an EF7 engine was measured at steady state and then the intended changes was implemented on the two ends of the cylinder head. After that, all valves sits' angle were fabricated in accordance with corresponding standards. Then, this method was experimentally evaluated using the flow bench test so that in addition to measure the accuracy of swirl flow, the swirl flow coefficient can be compared with other methods such as flow control valve. The results show that there is a minor reduction in flow coefficient for low valve lifts, but It can be gained an acceptable amount of swirl flow for high valve lifts with minor costs and changes for cylinder head in comparison with other designs.

In this study, the effect of fuel filter lifetime on the temperature of gasoline output from the fuel pump, ignition advance, injector injection pressure and electric current of the fuel pump of a gasoline engine was examined experimentally with the aim of improving the variables of fuel and ignition systems. The results of this study showed that the lowest temperature of gasoline output from the fuel pump and the amount of electric current of the pump using a new filter were 37.5 ˚C and 2.88 A, respectively. The highest temperature of gasoline output from the fuel pump and the amount of electric current of the pump, measured using a filter with a range of 60,000 km, were 40.5 ˚C and 4.12 A, respectively. The highest injection pressure of the injectors and the lowest amount of ignition advance at 1000 rpm engine speed and using the new filter were 3.5 bars and 7 degrees, respectively. The lowest injection pressure of the injectors and the highest amount of ignition advance at 5000 rpm engine speed by using a 50,000 km filter lifetime were reported as 2.5 bars and 37 degrees, respectively. It is lucid that filters with a lifespan of more than 15,000 km reduce the combustion quality and efficiency of the engine.

Today, vehicles are increasingly equipped with brushless DC permanent magnet motors due to the nature of sensorless operation. BLDC motor controllers can operate the effective speed and position control in a closed loop feedback system without a position sensor mounted on the shaft. The fractional order PID controller is one of the most common examples of a feedback control algorithm used in many control processes. The BLDC sensorless motor drive has better optimal control over the rotor speed and accuracy with the help of PID fractional controller (FOPID). In this paper, using two meta-heuristic optimization algorithms, the FOPID control parameters including sitting time, rising time, overload and step response stability of the mentioned system were optimized. The results show that the PMBLDC stepper motor response using the proposed genetic algorithm provides better control performance compared to other available methods.

The purpose of this study was to optimize the operational parameters of the electrical discharge machining (EDM) process in the Inconel 718 super alloy using the Taguchi method and analysis of variance (ANOVA). First, using Taguchi method, the optimal order of experiments was determined, and then by performing experiments and analysis of variance, the effects of the contribution of each input parameter on the process output were determined, and finally the optimal input parameters were determined. Input parameters in this study included pulse duration, work factor, gap voltage and discharge current. Furthermore, process output parameters, electrode wear ratio, material removal rate and topography of the sample surface were taken into consideration. From the surface topography point of view, items such as surface roughness, recast layer thickness and crack density of machined samples were studied in detail. In addition, modeling and regression analysis was performed to predict the behavior and values of process output parameters. The results of optimizing the operational parameters of the process indicated less electrode wear, better surface roughness and homogeneous and crack-free microstructure compared with the behavior of the Ti-6Al-4V alloy.

The main aim of this research was to experimentally investigate the two coupled identical ST500 gamma-type Stirling engines and convert thermal energy to cooling energy. Using a new structure and two coupled Stirling engines at different temperatures and pressures and use of biomass fuel within the 4 -8 bar average pressure range of the first engine hot source, the 1-4 bar average pressure range of the second engine cold source, and Stirling hot engine temperature range of 480-580 ºC, the effective cooling is obtained in the cold engine. In doing tests, attempts were made to reach lower than 9 percent error results in different parts of engine, including insulation, fluid leakage, belt loosing, and measurement devices. According to the obtained results, a 8 bar increase in the average pressure range of the gas in the first engine hot source, a 1 bar reduction in the average pressure range of the gas in the second engine cold source, the increased temperature of the hot source up to 580 ºC, and the use of the light operating fluid such as helium will affect the generation of cooling up to -16ºC.

The increasing growth of construction and use of concrete tables in urban and inter-city roads have led to the idea of ​​using recycled concrete in urban concrete tables. Therefore, in this research, an attempt was made to investigate the mechanical and economic parameters of using recycled concrete as concrete of urban concrete tables. For this purpose, three types of mixing schemes of natural concrete as control concrete, recycled concrete and recycled fiber concrete including 100% recycled fine-grained and 50% coarse-grained recycled concrete of 7 and 28 days old were tested. Then, the obtained results were compared with national and international regulations and standards in the field of concrete for use in urban tables. In addition, in this paper, the estimation of 28-day compressive strength with the help of neural networks was investigated. The findings showed that recycled concrete and recycled fiber concrete with higher mixing design have higher compressive strength. Furthermore, an almost equal correlation coefficient was observed in the outputs of the 28-day compressive strength test obtained from the artificial neural network and the results of 124 laboratory samples are in good agreement with the results obtained from the neural network.

Nowadays one of the challenges that engineers and structural designers encounter is reduced vibrations of structures due to lateral forces such as earthquakes and winds. Taking into consideration that the design and construction of tall buildings is one of the most common methods of land-use in highly populated urban areas, the necessity and importance of identifying methods of controlling structural vibrations is felt more keenly than before. One of the methods of structural motion control is passive structural motion control with friction dampers. In this study, the main focus on the application and performance of friction dampers is new ideas for using the friction phenomenon to control structural vibrations and the design challenges of structures with friction dampers. For this purpose, first, we try to point out the important concepts in vibration control. Then, the goals, methods and results of various existing researches are examined to provide a clear view of friction dampers for structural engineers and as a start for future research to develop and improve the performance of friction dampers.

In this study, Sendust alloy (Fe85Si9.6Al5.4) was fabricated by the mechanical alloy method. The obtained alloy was annealed for 2h at 1100 ͦC in the Ar atmosphere. Phase identification and morphology analysis of the milled and annealed powders were performed by X-ray diffractometer and scanning electron microscope, respectively. The results showed that the Sendust nanostructure solid solution obtained after 10h milling and after annealing the grains grew. The resulting alloy was insulated with sodium silicate adhesive and then mixed with various percentages of Zn- stearates from 0.25 to 0.75wt. %. These composites were formed by PM-method at 1600 MPa to obtain magnetic powder cores. The real and imaginary part of effective permeability and quality factor of the cores were measured with an LCR-meter. In addition, the results indicated that the green density of the core with 0.5% Zn-Stearate was higher than that of 0.25% Zn-Stearate and then remained constant. The magnetic properties of the sample were also optimized with 0.5% stearate. A comparison of the real part of permeability for the core with the unannealed and annealed powders showed that annealing of the powders resulted in an increase in the permeability and increased the Q-factor to frequencies below 200 kHz.

Split ring resonators (SRR) are suitable for microwaves due to their unique properties. In this research, using metamaterials and SRR structures, a band-pass filter on the C band was designed. The main filter structure consisted of two SRRs connected with a microstrip line. The initial size of the structure, such as the radius of the rings, was estimated based on the central wavelength of the filter. In order to increase the bandwidth and the efficiency of the passage in the central frequency, genetic algorithm was used and the optimal dimensions of the filter were obtained. The change in the central frequency of the filter due to the change in the dielectric constant was investigated, and the filter stability was depicted in relation to the change in its dimensions. Compared to other existing filters, this filter, with its simplicity of structure and ease of construction, has better characteristics such as a high pass ratio at center frequency and wide bandwidth.

The effect of magnetic hyperthermia on dissolution of cobalt ferrite nanoparticles in distilled water was investigated. Synthesis of cobalt ferrite nanoparticles (CoFe2O4) was performed by Co-precipitation method at 80 ° C, with precursor including iron and cobalt salts in the presence of air atmosphere. CTAB was used as a surfactant in this synthesis. The particle structure and morphology as well as the structure and magnetic properties of these nanoparticles were studied by X-ray diffraction (XRD) field emission scanning electron microscopy (FESEM) and vibrational sample magnetometer (VSM), respectively. Sample magnetic hyperthermia was measured after preparation of ferrofluid with a concentration of 3 mg/ml in distilled water and in an ac magnetic field with a frequency of 400 kHz and a field intensity of 400 Oe. The increase in sample temperature over time was determined and its specific heat dissipation power (SLP) was measured. According to the measurement results, the sample SLP was 151 W/g.

The feasibility of joining AA6061 and AA5010 by FSW is one of main purposes of the current research. First, 9 experiments were conducted with aim of optimal pin profile design. These experiments were designed by using various straight cylindrical, square and triangular pin profiles under different frictional conditions. Results of the first stage indicated that the tool with square pin profile leads to the highest tensile strength, hardness and elongation. All process steps were simulated in finite element software and the results were analyzed. Hence, this tool was applied for conducting the second stage of experiments. Experiments of second stage were designed and performed with the aim of investigating the effect of tool rotary speed, welding speed and plunge depth on tensile strength, hardness and elongation and selection of optimal factors combination which result in maximal mechanical properties. In the second stage, the central composite design of experiments was used to conduct experiments and to model mechanical properties accurately and find the optimal solution, the neural network was integrated with particle swarm optimization (PSO). Results demonstrated that the neural network with topography of 3-11-3 yields superior prediction. In addition, tool rotary speed of 800 RPM, welding speed of 60 mm/min and plunge depth of 0.2 mm is the optimal combination that leads to maximal tensile strength, hardness and elongation.