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The Internet of Things (IoT) consists of sensors, networks, and services to connect and control production systems. Machine-to-Machine (M2M) communication technology is considered as a key underlying technology for building Industrial IoT environments where devices are enabled to exchange information with each other in an autonomous way without human intervention. Resource-Constrained Devices (RCD) have found an expanding demand in the Internet of Things (IoT) applications as these gadgets are essentially working with delicate information. Thus, information security has ended up vital for both makers and clients. However, the creation of defenseless gadgets still challenging regarding the restriction of involved assets especially with the attackers ‘continuous trials to misuse these restrictions chasing important information. Hence, connecting an open key crypto-system becomes a must to extend gadget proficiency and relieve the chance of touchy data loss. Deployments of Elliptic curve cryptography (ECC) are fundamentally an open key crypto-system with the basic distinction of speedier advancing capacity whereas yielding an assortment of distinctive approaches to the arrangement of the cryptographic calculation. We will submit a proposed protocol to overcome the demands of information security and the speed of data circulation. The proposed protocol is characterized by low computational cost, communication and storage overhead, while achieving mutual authentication, session key agreement, device’s identity confidentiality, and resistance against various attacks.

A conventional photovoltaic (PV) system driving a DC load consists. of a PV array ,storage battery. a battery voltage regulator (BVR) and a load The voltage of typical lead acid batteries. widely used in PV systems, varies between 93 5 % and 120% of its nominal voltage according to its state of charge (SOC) such voltage variations are not accepted for critical loads such as some communication systems Conventional solution of this problem is to operate the PV system at higher voltage and to include a control circuit that introduces passive elements so that the load is operating within the allowed limits. Such a solution leads to power dissipation in the passive elements and this presents power toss. In this work an alternative solution based on a microprocessor that keeps the load voltage at the predetermined level is discussed. The system consists of an A/D converter, a microprocessor controller, a switching circuit and a filter. The microprocessor reads the battery voltage variations via the A/D converter corresponding duty cycle value is calculated and used to control the switching circuit to achieve the required regulation. A detailed simulation program is used to study the performance of the PV system installed in Cairo city. The proposed technique avoids the power loss and as a result the required PV array size becomes smaller. Hence the system economics is improved.

Detection of liquid level in large tanks is presented in this paper. The liquid level is detected using a transmitter and RFID tag antennas as a receiver. The transmitter antenna is a Vivaldi with wide bandwidth from 0.5 GHz to 3 GHz. The Vivaldi antenna is fabricated on FR4 with 𝜀𝑟 = 4.3 and thickness of 0.8 mm. Two conformal RFID tag antennas are used as receiver antennas. The conformal antenna is placed on Rogers Ultram 3850 flexible substrates with 𝜀𝑟 = 2.9 and a thickness of 0.1016 mm. The conformal antenna is designed to set on a cylindrical tank made from PVC material. The first tag works at 0.9 GHz and the second tag works at 2.45 GHz. Water and Oil are used as liquids for testing. The antennas are simulated using CST microwave studio simulator Ver.14. The system is also fabricated and measured. Good agreement is achieved between simulated and measured results.

In this paper, a switched beam antenna system consists of four Vivaldi antennas for vehicle-to-vehicle communication is presented. The proposed design is realized on a substrate material of “Rogers 5880” with εr=2.2,tanδ=0.002,andεr=2.2,tan⁢δ=0.002,and0.508-mm substrate thickness. The antenna is designed to operate at a center frequency of 28 GHz with operating bandwidth of 1.463 GHz. An overall realized gain of 9.78 dBi is achieved at the intended center frequency. The proposed antenna is designed and simulated using CSTMWS. It is also fabricated using photolithography techniques and measured using R&S vector network analyzer. Good agreement is obtained between both CSTMWS and measured results.

This paper proposes a safe and effective method to generate the subkeys that are used in the Advanced Encryption Standard (AES) algorithm for data encryption applications. The suggested method relies upon the Pseudo-Random Number Generator (PRNG) that is created from the improved Lorenz chaotic system. The output of PRNG is exploited as a key schedule for generating AES subkeys where the output is characterized by having an infinite periodic length. This method can be used in high-speed applications since no hardware multipliers are utilized so it gives the best hardware performance. Simulation and Synthesis of the suggested method are done by using the ISE 14.7 and analyzed by MATLAB and the NIST mathematical suite that was included, this method only made use of 4% from the Virtex 5 FPGA kit's slices and operating frequency reached a maximum of 242MHz.

Reduced graphene oxide and polyaniline (RGO-PANI) composite was prepared via functionalized ferrite on graphene oxide as corresponding PANI nucleation sites, which dramatically increase the composite specific capacitance and lifetime when compared with crude PANI. Symmetric paper-based supercapacitors (SCs) were fabricated and electrochemically tested using different electrolytes namely; KOH, H2SO4, H3PO4 and Na2SO4. Therefore, strong alkaline, strong acid, weak acid and natural electrolytes impact on the composite was studied. The influence of various electrolytes was studied intensively using Bio-Logic VSP-300 where cyclic voltammetry, Galvanostatic charge/discharge and impedance spectroscopy tests were applied. The highest achieved specific capacitance was more than 500 F/g of pure electric double layer behavior coupled with 100% retention after 5000 cycles. The composite was characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and transmission electron microscopy.

Much attention has been focused on the role of UAVs in wireless networking due to their increasing use in unmanned aerial vehicles (UAVs). Until national laws allow unmanned aerial vehicles to fly independently, we will see large numbers of UAV swarms performing various tasks in the intelligent cities, including package delivery, facility management, event filming, monitoring and tracking. 5G/B5G mobile networks will benefit the UAV environment, and it can be used to enhance UAV communications in a variety of ways. UAVs' features of versatile mobility in 3D space, as well as autonomous operations and intelligent positioning, accommodate a wide range of wireless technologies and applications. This paper is meant to detail how 5G/B5G mobile systems and UAV technology merge to offer both enhanced aerial mobility and increased data capabilities for mobile users (UE). Cellularly linked UAVs play the role of cellular flying consumers, and are referred to as UAVs with a direct connection to consumers (a.k.a. UAV-UE, drone-UE, 5G-connected drone, or aerial user). This project's focus is to assemble an in-depth task analysis along with essential technical advancements in 5G/B5G and on-going field trial and prototyping work on cell-based UAVs. This report details recent developments within the 3GPP organisation and presents social and economic issues that must be taken into consideration before a successful introduction of this potentially useful technology. Accessible issues are already present and pave the way for future opportunities.

In this paper, the marine predator algorithm (MPA) is proposed for solving transcendental nonlinear equations in a selective harmonic elimination technique using a multilevel inverter (MLI). It proved its suitability and supremacy over the other selective harmonic (SHE) techniques used in recent research as it has good precision, high probability of convergence, and improving quality of output voltage. The optimum values of switching angles from MPA are applied to control a three-phase 11-level MLI using cascaded H-bridge (CHB) topology to control the fundamental component and cancel the low order harmonics for all values of modulation index from 0 to 1. Analytical and simulation results demonstrate the robustness and consistency of the technique through the MATLAB simulation platform. The results obtained from simulation show that the MPA algorithm is more efficient and accurate than other algorithms such as teaching-learning-based optimization (TLBO), flower pollination algorithm (FPA), and hybrid particle swarm optimization with gray wolf optimization (PSOGWO). A prototype for a three-phase seven-level cascaded H-bridge inverter (7L-MLI-CHB) experimental setup is carried out. The output of this experimental test validated and supported the results obtained from the simulation analysis. The model of power loss of three-phase 7L-MLI-CHB using the silicon metal-oxide-semiconductor field-effect transistor (MOSFET) is obtained according to the modulation technique. Conduction and switching losses are calculated based on the experimental manufacturer data from the Si-MOSFET using the thermal model of Piecewise Linear Electrical Circuit Simulation (PLECS). Losses and output power are measured at different modulation index values based on the MPA algorithm. Finally, a design of heatsink volume is presented for this design at different temperatures.

The widespread adoption of network function virtualization (NFV) leads to providing network services through a chain of virtual network functions (VNFs). This architecture is called service function chain (SFC), which can be hosted on top of commodity servers and switches located at the cloud. Meanwhile, software-defined networking (SDN) can be utilized to manage VNFs to handle traffic flows through SFC. One of the most critical issues that needs to be addressed in NFV is VNF placement that optimizes physical link bandwidth consumption. Moreover, deploying SFCs enables service providers to consider different goals, such as minimizing the overall cost and service response time. In this paper, a novel approach for the VNF placement problem for SFCs, called virtual network functions and their replica placement (VNFRP), is introduced. It tries to achieve load balancing over the core links while considering multiple resource constraints. Hence, the VNF placement problem is first formulated as an integer linear programming (ILP) optimization problem, aiming to minimize link bandwidth consumption, energy consumption, and SFC placement cost. Then, a heuristic algorithm is proposed to find a near-optimal solution for this optimization problem. Simulation studies are conducted to evaluate the performance of the proposed approach. The simulation results show that VNFRP can significantly improve load balancing by 80% when the number of replicas is increased. Additionally, VNFRP provides more than a 54% reduction in network energy consumption. Furthermore, it can efficiently reduce the SFC placement cost by more than 67%. Moreover, with the advantages of a fast response time and rapid convergence, VNFRP can be considered as a scalable solution for large networking environments.

System sizing is necessary for evaluating the PV system as first step before investing at a given project. However, there is a lack of developing MATLAB code for grid-connected system to present a techno-economic solution taking into consideration the less running time and covering our local needs. This paper aims to develop a pre-sizing offline tool using MATLAB software. Moreover, the developed code is integrated with tariffs and electricity bills for both low and medium voltages including all sectors. Furthermore, the tool is applied for all applicable areas like rooftop industrial shed and ground mounted. Hence, Egypt was applied in this tool through selecting four locations Cairo, Alexandria, Aswan and Hurghada. Case studies were sized using MATLAB code and validated by PVsyst, as result the percentage of error ranges from 1 to 6%. Additionally, developed code shows the capability of giving a full techno-economic solution in preliminary design stage. The results showed that Aswan was the best location for installing PV system technically and economically where the highest specific yield and capacity factor recorded were 2062 kWh/kWp/year, 24% respectively. Moreover, the lowest levelized cost of energy and simple payback period 0.56 EGP/kWh, 4.3 years respectively were recorder in Aswan.

This paper presents a novel conformal monopole antenna used for liquid level identification in tanks. Designing RFID tag antenna on a liquid detection is challenging due to the relative permittivity, high conductivity and the diversity of liquids. A comparison between planar and conformal designs has been done using a CST microwave studio simulator. The antenna has been fabricated on Roger 3850 flexible substrate material. The conformal Antenna has been designed to work on a cylindrical tanks made of PVC material. The proposed antenna resonance frequency is shifted forward from the planar antenna at 0.9 GHz to 0.8 GHz in conformal design. The impedance bandwidth is 0.29 GHz where a planar antenna gives bandwidth 0.35 GHz. The antenna gain is 2 dB in case of conformal antenna while is 2.28 dB in case of planar design.

Radio wave propagation can be characterized by two major sets: empirical and deterministic models. Empirical models rely on the received signals’ statistics and thus offer lower precision. Deterministic models have certain physical bases and therefore necessitate a massive amount of geometrical data. For instance, the ray-based technique represents a suitable facility for reliable estimations in indoor schemes. Ultra-wideband (UWB) technology allows transmitting signals over a huge bandwidth, typically in the order of 500 MHz to several GHz enabling the design of communication systems with very high data rates. Massive multiple-input multiple-output (MIMO) is a new technique, utilizing a large number of base station antennas, advancing large system capacities in multiuser schemes, where multiple users are simultaneously served in the same time-frequency resources. We develop a ray-based procedure to investigate the behavior of the downlink UWB massive MIMO channel including the antennas transfer functions under various typical propagation situations. We estimate the magnitude and the phase of the voltage induced at each receiving antenna as a function of frequency (through the reciprocity theorem). We compare the singular value spread (SVS) cumulative distribution function (CDF) of each situation while varying the number of base station antennas. As the number of base station antennas or the inter-user separation increase, both the SVS and the sum-rate improve, the channel becomes more favorable , where better spatial separation is provided, and the disparity of the power values allocated for the users’ channels reduces (through water-filling). The attained monotonic sum-rates were verified with the interference-free sum-rate.

Massive multiple-input multiple-output (MIMO) is a breakthrough technology advancing huge network capacities in multiuser scenarios in which a base station (BS), with a large number of antennas, simultaneously serves multiple users in the same time-frequency resources. We study the massive MIMO channel behavior through the channel matrix singular value spread (SVS), users’ channels correlation, and sum-rate. As the inter-user spacing or the number of BS antennas increase, the sum-rate, SVS and inter-user correlation enhance and the users’ channels can be easily separated. Concerning the duplexing transmission schemes, in time division duplexing (TDD) mode, the entire bandwidth for both uplink and downlink is utilized and the propagation channel reciprocity can be used where the amount of resources needed for pilots only depends on the number of simultaneously served terminals. However, in frequency division duplexing (FDD) systems, which are widely deployed because of their existing spectrum assignments, the uplink and downlink channels are at different frequencies and thus are not reciprocal where a considerable amount of feedback overhead is required. Our central objective is to exploit the directional spatial correlation for the uplink and downlink channels, based on the structure of their multipath clusters, to estimate the downlink channel for an FDD system. The proposed method uses the spatial correlation between the uplink and downlink where the clusters are deduced from the uplink channel. Then, the phase of the signal arriving at the BS is modified to construct the signal departing from the BS and hence the downlink channel can be estimated.

In the last decades, the use of renewable energy resources instead of fossil fuels pollution has increased exponentially to overcome the rapid growth of energy demand. This paper, presents a Perturb and Observe (P&O) algorithm and Incremental conductance technique for extracting the maximum power from a stand-alone PV for use in pumping system. The PV system comprises a solar panel, DC-DC boost converter, MPPT and permanent DC motor driving a Centrifugal pump. Results are accomplished by modelling and simulating the complete MPPT with PV pumping system using MATLAB/Simulink .MPPT algorithms performance is measured to confirm its significantly improved power extraction performance under different sunlight condition.

This research provides a complete analysis of photovoltaic (PV) inverter of 3kW output power by merging the design of PV array and DC-AC inverter; The design includes a PV module to configure a large array that agrees with the inverter power output, the DC-DC step-up (boost) converter, next the full-bridge using MOSFET switches controlled by PWM (Pulse Width modulation) is used to generate three levels signal and the output LCL filter design, then to the load. Also studying the inverter parameters that affect the losses and inverter efficiency. The design is verified using Matlab-Simulink simulation using parameters of a real PV module, switches and passive elements to be close to practical work. The simulation results prove the design output consistency.

Despite the advantages and importance of conventional linear regulators, low efficiency of about 40% is one of the main corresponding drawbacks. Supercapacitor assisted low dropout regulator (SCALDO), a linear DC to DC technique that can be used to duplicate efficiency. Therefore, supercapacitor is playing a crucial role to maximize the efficiency as a result of nearly lossless voltage dropper element, which minimize the losses in the pass element and power semiconductors. This work represents the mathematical principles of SCALDO and a simple implementation with simple and costly effective electronic components contrary to the traditional techniques. The proposed low dropout regulator is used to convert 12V to 5V. The linear regulator based on high efficiency SCALDO technique makes it appropriate for solar cell power systems applications.

Massive multiple-input-multiple-output (MIMO) system enhances area throughput by achieving high spectral efficiency. Pilot contamination limits the system performance. In this paper, we propose a pilot reuse factor adoption and applying multi-cell minimum mean square error (M-MMSE) precoding/combining scheme under the assumption of Laplacian correlation model to mitigate pilot contamination. Simulation results show that the proposed scheme outperforms the other existing precoding/combining schemes in decontaminating pilots and achieving larger spectral efficiency. The price to pay for interference rejection and spectral efficiency improvement is a small reduction in the desired signal power and an increase in the system computational complexity.

This paper presents an optimum design of the solar Photo-Voltaic (PV) power system for small Geostationary Earth Orbit (GEO) satellites using triple junction solar cells and advanced Lithium Ion batteries. The paper applies the proposed system on various propulsion technologies; full chemical, full electrical and hybrid propulsions. This research work studies the capability to fulfil efficiently all the satellite power requirements during both the launching and the on-station phases while reducing the high cost challenge. Since the propulsion type is a key factor for the satellite cost, an economic analysis is demonstrated and investigated in two different strategies. The first scenario fixes the satellite weight and offers the revenue due to the increase in the satellite payload. However, the second scenario evaluates the saving profits due to the reduction in the satellite weight using the same number of satellite transponders. The analytical comparison among the different propulsion techniques shows the superior advantages of using the full electrical satellites.

Unmanned aerial vehicles (UAVs) have sparked a lot of interest in the wireless networking community as an emerging subject in aerial robotics. The UAV environment can be used to improve UAV communications in various ways. These smart devices cater for a broad variety of wireless technologies and applications because of UAV's inherent features related to versatile mobility in 3D space, autonomous operations as well as intelligent positioning. This study will investigate the convergence synergies between 5G/B5G mobile systems and UAV technologies, with the UAV being integrated into current cellular networks as a modern aerial user equipment (UE). In this integration, UAVs play the function of cellular flying customers, and are hence referred to as cellularly linked UAVs (a.k.a. UAVUE, drone-UE, 5G-connected drone, or aerial user). The major goal of this research is to provide a thorough analysis of the integration task, as well as major technical breakthroughs from 5G/B5G and current work in prototyping architecture and field trials that support cell-based UAVs. This study examines recent 3GPP standards advances as well as socio-economic challenges that must be addressed before this promising technology can be properly implemented. There are already some accessible issues clearing the way for potential study opportunities.

This paper presents modeling for an air-to-air guided missile. The model describes a detailed missile system including the aerodynamics of the missile, the set of equations of motion and the autopilot. Possible tactical situations are applied on the model and included in the paper. System identification is also carried out to help in our research goals which include designing a new controller that takes into consideration the problems we faced using the current one. Our design is in a modular form based on previous work which is the base for a lot of missile systems’ simulation software. Our model was designed using Simulink and MATLAB environments. Our work is characterized by using classical controller as an autopilot instead of complex controllers and maintaining accepted results in many possible tactical situations.

Whispering gallery modes are those modes propagating the long of curved structures, spheres in our case. They have found numerous applications at optical frequencies in applications like sensors, filters and resonators for microlasers. Of special interest is their use to increase light absorption when sustained in dielectric nanospheres on top of thin film solar cells. Since these modes have very complicated mathematical forms, numerical solutions are used to characterize them. In this letter, we present an innovative fast all numerical technique to calculate the eignwavelengths of the modes inside a nanosphere. The obtained results are in very good agreement with the analytically calculated values.

The Partial Shadowing (PS) is one of the hotspot topics and one of the significant challenges in the Photovoltaic (PV) systems. The PS of PV modules cause serious energy loss of the PV energy. It is observed (using detailed simulation MATLAB programs) that, The PS effect is clear on both of I-V & P-V output characteristics (Ch/s) curves. Also, it is observed that, the energy loss due to PS when no diode is used is significantly large. But when the diodes are used, the energy loss decreases appreciably. The saving in energy loss increases as the number of diodes per module increases. It is proposed here to increase the number of diodes per each group of solar cells results in saving of energy loss. This Paper shows the recommended number of bypass diodes (Internal or External) solution to reduce the energy loss. The internal solution by increasing of diodes number per module, while the external solution by increasing of diodes number per group. This paper also discusses the effect of increasing the operating voltage of the system on PS loss.

Thin film solar cells (TFSCs) where first introduced as a low cost alternative to conventional thick ones. TFSCs show low conversion efficiencies due to the used poor quality materials having weak absorption capabilities and to thin absorption layers. In order to increase light absorption within the active layer, specially near its absorption edge, photon management techniques were proposed. These techniques could be implemented on the top of the active layer to enhance the absorption capabilities and/or to act as anti-reflecting coating structures. When used at the back side, their purpose is to prevent the unabsorbed photons from escaping through the back of the cell. In this paper, we coupled the finite difference time-domain (FDTD) algorithm for simulating light interaction within the cell with the commercial simulator Comsol Multiphysics 4.3b for describing carrier transports. In order to model the dispersive and absorption properties of various used materials, their complex refractive indices were estimated using the Lorentzian-Drude (LD) coefficients. We have calculated the absorption profile in the different layers of the cell, the external quantum efficiency and the power conversion efficiency achieved by adding dielectric nanospheres on the top of the active layer. Besides that, the enhancement observed after the addition of dielectric nanospheres at the back side of the active layer was computed. The obtained results are finally compared with the effects of using textured surface and nanowires on the top in plus of cascaded 1D and 2D photonic crystals on the back.

With the current shift towards low-voltage low-power applications, static random access memory (SRAM) cells are being operated at very-low supply voltages near the threshold voltages of the transistors. This imposes severe design challenges for conventional 6T SRAM cells. This paper presents a new quantitative analysis for the read, write, and hold noise margin of SRAM cells when operated at near-threshold voltages capturing transistor short-channel effects. Using the derived equations, an optimal design methodology is introduced to yield the SRAM cell size at a certain supply voltage for best noise-margin performance. This optimal design is verified by circuit simulations for a 6T SRAM cell implemented in 65-nm CMOS technology.

Efficient network resource sharing in cloud computing environments is a challenging problem. Additionally, network congestion has been reported as a main bottleneck in multi-tenant data centers. In this paper, the problem of virtual machines allocation is tackled based on Software-Defined Network (SDN) resource allocation strategy. Moreover, several important parameters are taken into consideration that have been ignored in previous related studies. Another important imposing goal of this paper is to minimize the overall cost in cloud computing environments while allocating network resources. Simulation studies have been conducted to evaluate the performance of the proposed strategy. Simulation results show a reduction in the utilization in the valuable upper-layer links in data centers which is resulted mainly from favoring the lower-cost links during the allocation process. Additionally, the proposed strategy is able to cope with the dynamic nature of allocation process. More importantly, it avoids false allocation in cloud computing environments.

Nowadays the world became filled by several vulnerable problems that need to a quick solution and occupies the thinking of most people. From these problems the Road Network traffic crises that produces congestion, collision and … etc, thus a lot of issues are effected, such that working times, people psychology and so on. So we need to find an effective solution under the world financial crisis circumstances and surrounding environment, means that a solution achieve low cost, where from the suggested solutions for reducing or facilitation the traffic motion problems mainly are depending on the mobile communication (cell phone, GPS, Satellite… etc.), but it need to more funding. We find that the Data Network can perform the wanted aim due to the fast development nowadays of the computer systems and technologies, where we look forward to reach to certain model based on complete mapping between all Road Network parameters and the corresponding in the Data Network. This paper will discuss a mapping between Road Network parameters and Data Network parameters that will be used to get the model.

Virtual machine provisioning in multi-datacentre cloud computing environments is a challenging problem. However, most current virtual machine management strategies ignore their effect on cloud network. In this paper, a scalable network-aware resource allocation strategy is proposed that dynamically allocates virtual machines in cloud computing environments while minimising the overall cost. It is mainly utilised at the cloud service provider that has a large number of datacentres. Several important parameters have been taken into consideration that are mainly ignored in previous related studies. Additionally, software-defined network (SDN) has been adopted in the proposed strategy. Simulation studies have been conducted to evaluate the performance of the proposed strategy. Simulation results show a reduction in the utilisation in the valuable upper-layer links in datacentres that resulted mainly because of favouring lower-cost links during virtual machine allocation process. Additionally, the proposed strategy is able to cope with the dynamic nature of the allocation process.

In order to develop an optoelectronic model for simulating different light trapping structures sandwiching the photovoltaic active layer, determining the materials dispersion and absorption properties is a must. The targeted model should be able to simulate the desperation and absorption capabilities of different conductor and semiconductor materials over the entire sun spectrum (200 nm to 1700 nm). Therefore, the Lorentzian-Dude (LD) model is chosen due to its simplicity in implementation with the finite difference time domain algorithm chosen for optical modelling. In this paper, various materials are selected to be modelled with the LD model. The proposed algorithm is not only used for modelling material behaviour of various conducting materials published in literature, but is also used for other conducting and semiconducting materials that the original model was not capable of modelling over the entire range of spectrum. Besides that, the suggested algorithm showed a better time performance than those mentioned in literature. Experimental 1D grating structure prototype samples were made to validate the simulation results, showing perfect agreement.

A novel structure for thin-film solar cells is simulated with the purpose of maximizing the absorption of light in the active layer and of reducing the parasitic absorption in other layers. In the proposed structure, the active layer is formed from an amorphous silicon thin film sandwiched between silicon nanowires from above and photonic crystal structures from below. The upper electrical contact consists of an indium tin oxide layer, which serves also as an antireflection coating. A metal backreflector works additionally as the other contact. The simulation was done using a new reliable, efficient and generic optoelectronic approach. The suggested multiscale simulation model integrates the finite-difference time-domain algorithm used in solving Maxwell’s equation in three dimensions with a commercial simulation platform based on the finite element method for carrier transport modeling. The absorption profile, the external quantum efficient, and the power conversion efficiency of the suggested solar cell are calculated. A noticeable enhancement is found in all the characteristics of the novel structure with an estimated 32% increase in the total conversion efficiency over a cell without any light trapping mechanisms.

A conventional photovoltaic (PV) system driving a d.c. load consists of a PV array, storage battery, a battery voltage regulator (BVR) and a load. According to this arrangement, the load voltage is equal to the battery voltage. The battery voltage varies according to its state of charge (SOC). The voltage of typical lead-acid batteries, widely used in PV systems, varies between 93.5 and 120% of its nominal voltage according to its state of charge. Such voltage variations are accepted for many d.c. loads. However, critical loads, such as some communication systems, require a regulated voltage, hence such battery voltage variations are not accepted for these applications. The conventional solution of this problem is to operate the PV system at a higher voltage and to include a control circuit that introduces passive elements so that the load is operating within the allowed limits. Such a solution leads to power dissipation in the passive elements and this presents power loss. In this work, an alternative solution based on a microprocessor that keeps the load voltage at the predetermined level is discussed. The proposed technique avoids the power loss, and as a result, the required PV array size becomes smaller. Hence, the system economics are improved.

When photovoltaic (PV) systems are used to drive a.c. loads, d.c./a.c. inverters are necessary to convert the d.c. power to a.c. power. Dynamic a.c. loads, driven by single phase induction motors, require high starting current. It is known that the r.m.s. value of the starting current is about seven times the rated r.m.s. current of the motor. A theoretical and experimental investigation of the instantaneous starting current showed that it reaches values much higher than seven times the rated r.m.s. current. If the A/C is driven by an infinite a.c. source, such a high instantaneous current does not affect the source. However, if the A/C is driven by a PV array through an electronic inverter, such a high starting current can damage the electronic components of the inverter. In this work, a microprocessor-based control system to limit the high starting current is discussed. The proposed technique measures the rate of change of current and, hence, predicts the current at the forthcoming moments. According to this measured value, the microprocessor determines whether the A/C should be disconnected from the inverter or not. The microprocessor is programmed in such a way as to give the disconnect command before the current reaches the maximum allowable limit. The advance interval is equal to that needed to turn off the main electronic switch connecting the A/C to the inverter. Thus, the proposed control system guarantees a secure operation of the inverter. If the rate of change of the current is below a certain level, the current will be within the allowable limits, and the microprocessor system keeps the load connected to the inverter. The proposed microprocessor control system offers protection against the inrush starting current and keeps monitoring the motor current even after the starting period. If the motor current is accidentally increased during normal operation because of any problem, short circuit for example, the control system disconnects the motor from the source. Thus, the system provides continuous protection for the motor and the source.

The objective of a cathodic protection system (CP) is to protect the buried metallic structure against corrosion caused by chemical reaction between the buried structure and the surrounding medium, such as soil. Due to rains and humidity variations, soil resistivity varies, and consequently, the current supplied by a d.c. supply changes. To resolve this problem in conventional systems, the d.c. voltage of the supply is adjusted manually from time to time to keep a constant d.c. current. An elaborate automatic control system using a microprocessor is proposed in this work. Two alternative techniques are discussed. The first technique, like the conventional system, depends on measuring the voltage between the buried structure and a copper-copper sulphate cell at the assigned test points. The microprocessor controlled system proposed keeps the maximum and minimum voltages at the assigned test points within the allowed limits by changing the d.c. supply voltage. The second technique depends on sensing the d.c. load current. If the current changes due to environment variations, the microprocessor system adjusts the d.c. supply voltage in such a way that the d.c. load current is kept constant, regardless of environmental variations.