Scientia Iranica
Volume:29 Issue: 6, Nov-Dec 2022

Logic circuits in digital electronics can generally be classified two categories-combinational and sequential logic circuits.There are several software-based applications and hardware description languages to describe the structure and behavior of electronic circuits.Although it is an easy to construct a state transition table from the state transition diagram,creating an excitation table according to the memory element type in the sequential circuit design is a very laborious and time-consuming task.After the logic functions extracted from the state transition tables are obtained,logic design verification can be carried out by a conventional simulator.This will require time and persistence much like learning any other skill.Computer science degrees include courses focused mainly on programming languages.There’s a strong case to be made for use of skills acquired in programming courses to shorten the learning curve.Thus, this work has proposed a method for the implementation of the circuit only the state equations of the sequential circuit without dealing with excitation tables.This eliminates the process of constructing the circuit schematically, since it does not require flip-flop selection.In this method, since the state equations can be expressed through buttonbox,checkbox,textbox etc.which are the basic elements of the programming language,the behavior of the circuit can be observed in a very short time.

An accurate forecast of wheat yield prior to harvest is of great importance to ensure the sustainability of food production in Iran. The primary objective of this study is to determine the best remote sensing features and regression model for wheat yield prediction in Hamedan, Iran. In addition, the effects of various time windows on different regression models are verified. For this purpose, several vegetation indices (VIs) and reflectance values obtained from Sentinel-2, as input to regression models, are used in different time windows. As a result, Gaussian process regression (GPR) and random forest (RF) represented the top two best methods, and the best results were achieved for the GPR model with the SAVI, NDVI, EVI2, WDRVI, SR, GNDVI and GCVI indices corresponding to the image captured at the end of May. The best model yielded a root mean square error (RMSE) of 0.228 t/ha and coefficient of determination R^2 = 0.73. Moreover, different regression methods regarding the number of training data are compared. The neural network and linear regression were the most and stepwise regression was the model affected the least by the number of training samples. Experimental results provide a technical reference for estimating large scale wheat yield.

One of the most popular graphs in computational geometry is Yao graphs, denoted by $Y_k$, For every point set $S$ in the plane and an integer $k\geq 2$, the Yao graph $Y_k$ is constructed as follows. Around each point $p\in S$, the plane is partitioned into $k$ regular cones with the apex at $p$. The set of all these cones is denoted by ${\cal C}_p$. Then, for each cone $C\in {\cal C}_p$, an edge $(p,r)$ is added to $Y_k$, where $r$ is a closest point in $C$ to $p$. In this paper, we provide a lower bound of 3.8285 for the stretch factor of $Y_4$. This partially solves an open problem posed by Barba et al. (L.~Barba et al., New and improved spanning ratios for Yao graphs. Journal of computational geometry}, 6(2):19--53, 2015).

Having a reliable simulation tool for evaluating the performance of each design is indispensable. Designing multiple-valued logic (MVL) systems help to overcome the limitations existing in binary systems. Quantum-dot cellular automata (QCA) is a technology that can be substituted for CMOS in MVL designs. This paper represents an exquisite software platform for designing and simulating circuits which are restricted to three-valued logic (Ternary) quantum-dot cellular automata (QCA). Working with TQCAsim is so convenient because it can run in both Windows or Linux based computers. It has a tenacious simulation engine that can warranty precise results. This tool shows the results in graphical formats. As well, designers can easily layout their ternary QCA designs by using various sets of CAD tools. In this paper, the ternary model of QCA and its energy calculation will be demonstrated. The simulation Process will be explained step by step. MIN, MAX, NOT, and XOR gates had been simulated already by this software.

For decades, the electrical power grid worldwide has transformed from traditional to the smart power grid, focusing on its transparency to both utility and consumer. The energy management systems play a substantial part in demand response within the smart power grid umbrella, enabling demand-side management at the residential level. These systems generate the consumption profile of appliances and reduce the burden on end-user in scheduling appliances operations. With these consumption profiles of past usage, there is a possibility to generate a time window containing user preferable time slots for appliance operation for the next day. Using this time window, one can generate a cost-effective schedule-pattern autonomously. In this regard, this article proposes a home energy-demand management scheme consisting of a time window generator and a schedule-pattern generator to generate a cost-effectively comfortable schedule-pattern with demand threshold constraint. Multi-class appliances home enabled with a net-meter demonstrate the proposed approach's effectiveness. The simulation results showcase that the proposed approach helps the user to save electricity bills with constraint preserving comfort.

Nowadays, one of the most important criterions in designing different generations of cellular technology is to handle a large number of heterogeneous devices with high security guarantees. The first significant security issue considered in this field is mutual authentication of the devices and the network and authenticated key agreement between them. Hence, various authentication and key agreement (AKA) protocols were proposed for Long Term Evolution (LTE) and 5G networks. However, each of the protocols suffer from various security and performance problems. This paper proposes a group-based secure lightweight authentication and key agreement (GSL-AKA) protocol for machine-to-machine (M2M) communication. Security analysis and formal verification using the AVISPA tool prove that the proposed protocol overcomes various known security attacks and provides all the considered security requirements. Moreover, performance analysis shows that the communication and computation overheads of the proposed protocol are the lowest in comparison with the other existing group-based AKA protocols.

Parabolic carrier PWM method is considered as one of the direct current control methods which has been proposed for the voltage-source converters (VSCs). This method has an excellent dynamic response. Besides, it proposes a constant switching frequency by employing a pair of parabolic PWM carriers. However, it suffers from some drawbacks and limitations. The major drawback of this method is its sensitivity to the inductance variations. In other words, in grid-connected applications the exact value of grid inductance should be exactly known to achieve a proper performance from this method. Moreover, it is essential that during each switching cycle the voltage at the point of common coupling remains constant. In grid connected applications such as active power filter these drawbacks may lead to operate at variable or non-expected frequencies. Therefore, this paper concerns the suggestions to deal with the situation. In this paper, by applying the conventional method the aforementioned problems are examined in a grid-connected active power filter. It is shown analytically that by using the proposed method, problems of sensitivity to inductance changes and also necessity to constant voltage at point of common coupling in a switching period will be solved. Finally, simulation and experimental results are presented.

A novel, dual edge-shaped frequency reconfigurable antenna with a highly compact size is proposed, using microstrip line-based inset-feed mechanism. The presented antenna uses cost-effective ROGER substrate with a thickness of 0.787 mm and has been studied for its gain and radiation pattern in the radome structure presence. The antenna resonates within the range of 3 GHz to 9 GHz approximately, with maximum tuning efficiency of 43 % at 6.5 GHz, covering the major wireless applications of aviation service and wireless local area network (WLAN) in the upper segment of S-band along with worldwide interoperability for microwave access (WiMAX), long-distance radio telecommunications, and X-band satellite communication. The proposed antenna works resourcefully with a reasonable gain of 2.3 dBi at 5.04 GHz, significant bandwidth of 2800 MHz (maximum at 6.5 GHz), directivity, and reflection coefficient. The proposed multiband reconfigurable antenna along with radome structure using ABS material has been investigated under high-frequency simulation environment of HPEEsof of ADS (by Keysight Technologies) and 3d radiation pattern (far-field gain, directivity and power calculations) have been obtained using momentum and EMDS simulators of ADS. The final implementation size (without radome structure) for the patch design comes out to be 23 mm X 26 mm large.

Automatic Voltage Regulator (AVR) is employed to stabilize the output voltage of the generators in the electric power plants. However, reliable performance of AVR depends on professional tuning of its PID controller’s parameters. Therefore, different optimization algorithms are used to determine those parameters. The objective of the optimization is defined as minimizing the characteristics of transient step response such as settling time, rise time, overshoot, and steady state error. Then, to verify the optimization results, a simulator is built experimentally for AVR and PID system that can also be used for other studies on AVR systems. The experimental results are compared with those of MATLAB and Pspice Software. Close agreement between the simulation and experimental results confirms the success of the optimization.

Small wind turbines can generate clean energy in diverse locations, from urban centers to rural areas without access to the main grids. This study proposes design optimization of an axial flux permanent magnet (AFPM) synchronous machine for small scale portable applications. At first, a fast, accurate and pragmatic hybrid analytical model is proposed for performance prediction of the machine. The proposed model is then used as a basis for a direct search optimization process with factual constrains and objective functions to improve the machine in terms of efficiency, weight and to ease the manufacturing process. 3 Dimensional Time Stepping Finite Element Method (3-DTSFEM) is utilized to validate the accuracy and effectiveness of the proposed model and optimization methodology. Output characteristic of the machine from both analytical model and 3-DTSFEM are compared to each other that proves the functionality of the proposed study.

The paper presents a feasible way to construct the honeycomb structured microstrip antenna for UWB (Ultra Wide-band) applications with dual notch characteristic. The antenna designed based on the concept of initial stage of honeycomb nest construction and Defected ground structure(DGS) with dual notch for Ultra Wide Bandwidth applications. The two notches for WiMAX (3.5GHz center frequency) and WLAN (5.5 GHz center frequency) are introduced by etching two asymmetrical quarter wavelength slots in the ground. The compact antenna of size 12 x 20 mm2 with simple geometry achieves very wide bandwidth of 3.1-13.8 GHz(Covers UWB and higher frequency band) with dual notch characteristic.

Voltage control and Voltage stability are the most important issues in the power system. The purpose of this paper is to investigate the emergency voltage control in power systems. One of the most important proposed methods to solve this issue is optimal coordinated voltage control (OCVC), which is based on the model predictive control (MPC). Time limitations for preventing voltage collapse is the most critical constraint to solve an OCVC problem. In this paper, the Modified WARD-PV will be proposed to reduce the dimension of the power system and consequently, the speed of solving problem is increased. In this method, immediately after occurrence a fault, the power system is partitioned to into three subsystems by spectral graph partitioning method. Partitioning is based on reactive power flow through the lines. The subsystems, which are far from fault, will be replaced by the reduced model. This method will drastically reduce the number of system equations and will boost the speed of solving problem. The simulations results obtained on New England IEEE 39-Bus System reveals that the proposed method acts more precise than dimension reduction of power system based on linearization of external subsystems, but the speed of solving problem decrease.

Road luminaries are required to provide the luminance specified in the standards according to the road characteristics. For this reason, the light from the light source should be directed according to the desired conditions. While the range of minimum average road surface luminance recommended for different classes of road are provided; at the same time, it is desirable to be economical. In this study, a freeform lens and LED luminaire design with high luminous efficacy, low glare and uniform luminance distribution with a height of 1.5 m and a distance of 7 m between poles were designed for M3 road standards. First of all, lens design was made by using optical and illumination design software. Also, lens manufacturing and luminaire production were made as a result of the success of the design simulation test. The success of the LED luminaire in providing CIE standards has been measured on the designed road. In addition, the advantages and disadvantages have been determined by comparing with High Pressure Sodium Vapor (HPS) lamps.