The tribological and thermal properties enable iron based sintered materials with hard phase ceramic reinforcements as promising friction material for heavy-duty wind turbines. In wind turbines, the braking system consists of aerodynamic and mechanical braking systems. During application of mechanical brakes, the friction materials are pressed against the rotating low-speed shaft. The desired braking efficiency is achieved by utilizing a number of friction materials, which in turn are joined in a steel backing plate. Though this arrangement increases the braking efficiency, the hard phase ceramic reinforcement particles reduces the bonding strength between the friction material and steel backing plate. The joint failure leads to catastrophic failure of wind turbine. Therefore, the need of the hour is to develop friction materials with functional gradients that have high wear resistance (contact area) and high bond strength (interface). In this study, an attempt is made to fabricate and characterize a friction material with gradient profile of composition along the cross section to provide functional gradient property. The functional gradient friction material is synthesized by gradient deposition of Fe, Cu, Cg, SiC and fly ash powders which is then compacted and sintered. The prepared functional gradient friction material was characterized in terms of microstructure and microhardness. The tribological performance (wear rate and coefficient of friction) of the developed functionally gradient friction material was investigated at various loads using pin-on disc apparatus. The results show that as the load increases, the wear rate decreases and at the same time the COF tends to increase at higher loads. The predominant wear mechanism was deduced from the morphology of the worn surface.

This paper presents the indirect field vector control of induction motor (IM) which is controlled by an adaptive Proportional-Integral (PI) speed controller. The proposed solution can overcome the rotor resistance variation, which degrades the performance of speed control. To solve this drawback, an adaptive PI controller is designed with gains adaptation based on fuzzy logic in order to improve the performances of IM with respect to parameters variations, particularly the rotor resistance (Rr). The proposed control algorithm is validated by simulation tests. The obtained results show the robustness towards the load torque disturbances and rotor resistance variation of the adaptive Proportional-Integral fuzzy logic control with respect to classical PI control, and adaptive control based on rotor resistance observer.

Recently, many focuses have been done in the field of renewable energies, especially in solar photovoltaic energy. Photovoltaic generator, considered as the heart of any photovoltaic installation, exhibits sometimes malfunctions which involve degradations on the overall photovoltaic plant. Therefore, diagnosis techniques are required to ensure failures detection. They avoid dangerous risks, prevent damages, allow protection, and extend their healthy life. For these purposes, many recent studies have given focuses on this field. This paper summarizes a large number of such interesting works. It presents a survey of photovoltaic generator degradations kinds, several types of faults, and their major diagnosis techniques. Comparative studies and some critical analyses are given. Other trending diagnosis solutions are also discussed. A proposed neural networks-based technique is developed to clarify the main process of diagnosis techniques, using artificial intelligence. This method shows good results for modelling and diagnosing the healthy and faulty (shaded) photovoltaic array.

Numerical model of a corroded weld joint connecting pipe to flange using a finite element method was developed, and coupled with usual stress models. The structure material has been characterized experimentally. Monte Carlo simulations, FORM and SORM methods have been applied for estimating reliability and failure probability under corrosion and residual stress effects. A numerical case with various corrosion rates was conducted to determine the reliability of the welded connection pipe to flange. The obtained results show that the heat affected zone is very sensitive to corrosion effects due to the welding process.

In this study, a medium frequency power transformer has been designed analytically and its sizes have been obtained. The transformer’s analyses were made numerically by 2D AnsysMaxwell Solver software package. The Solver has also helped to study suitable transformer core and winding samples. Unlike medium frequency transformer, which is generally driven by unipolar PWM method, the designed transformer is driven by bipolar PWM method in the study. The core losses were obtained for different core materials (Trafoperm N3 and Amorfous 2605SA1) by AnsysMaxwell numerical and analytical calculations. The calculated losses for no-load working conditions were compared with each other. The designed transformer has been analyzed for its noload and loaded working conditions magnetically. Finally, the radial and axial forces created in the windings have also been examined for loaded working condition.

An ultra low power mixer with out-of-band radio frequency (RF) energy harvesting suitable for the wireless sensors network (WSN) application is proposed in this paper. The presented mixer is able to harvest the out-of-band RF energy and keep it working in ultra low power condition and extend the battery life of the WSN. The mixer is designed and simulated with Global Foundries ’ 0.18 μ m CMOS RF process, and it operates at 2.4GHz industrial, scientific, and medical (ISM) band. The Cadence IC Design Tools post-layout simulation results demonstrate that the proposed mixer consumes 248 μ W from a 1V supply voltage. Furthermore, the power consumption can be reduced to 120.8 μ W by the out-of-band RF energy harvesting rectifier.

The importance of conducting adequacy assessments of standalone systems with integrated renewable generation sources is growing. In this work, the focus is placed on the reliability assessment of an isolated microgrid operating on renewable energy generated by wind turbines (WTs) and photovoltaic (PV) panels. Batteries for storage were included in the model because of their crucial role in the system’s feasibility. Additional micro-gas turbines (MGTs) served as conventional backup. The sequential Monte Carlo simulation (SMCS) method was used to carry out simulations of the system, which was modeled using Markov matrices. Input data, such as wind speed, solar irradiance, and ambient air temperature, were used to simulate the power outputs of the generators. These historical data were fitted into appropriate distributions to extract corresponding parameters when simulating essential key factors necessary to produce the renewable power generation models. The adequacy model of the MGTs was obtained by employing the two-state reliability model, which was also superimposed with the generation models of WTs, PV panels, and batteries. The IEEE Roy Billinton test system (RBTS) was used for demand modelling. Common reliability indices were computed, and the system availability margins were evaluated.

In this paper, a six-channel microstrip diplexer is designed and fabricated. It operates at 0.75/0.85/1/1.25/1.6/1.8 GHz for multi-service wireless communication systems. It consists of two stub-loaded resonators, which are integrated by coupled lines. The channels are close together, which makes the proposed diplexer suitable for frequency division duplex (FDD) schemes. The proposed structure has a compact size of 0.025 λg2 where λg is the guided wavelength calculated at 0.75 GHz. The other advantages of the introduced multi-channel diplexer are the low insertion losses of 1.62/1.27/0.43/0.53/1.26 and 1 dB, as well as good return losses of 26/26/25/25/21.7 and 22 dB at 0.75/0.85/1/1.25/1.6/1.8 GHz respectively. A good isolation of less than 22 dB is obtained between the channels. In order to design the presented diplexer a designing technique is used which is based on the proposing of an equivalent approximated LC model and calculating the inductors and capacitors. To confirm the simulation results, the introduced diplexer is fabricated and measured.

In this work, similar and dissimilar friction stir welds of AA2024 and AA7039 were formed using optimized process parameters and truncated threaded tool. Characterization of weld joints for mechanical and microstructural properties was performed by tensile test, micro hardness test, optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. The tensile strength of similar joints was higher than dissimilar joints despite lower microhardness of former. Fracture of FSW joints was found to be started by the fracture of strengthening precipitate θ or η or both in the region of tensile fracture. Dissimilar joints and similar joints of AA7039 exhibited ductile fracture mode while similar joints of AA2024 showed brittle fracture mode.

Recently the proliferation of digital videos has increased exponentially due to availability of consumer cameras . Despite the improvement in the sensor technologies, one of the fundamental problems is that of noise affecting the video scenes. Recently, adaptive, pixel-wise, temporal averaging methods can advocate in denoising videos. In this work, we adapt the edge maps of frames within temporal averaging to guide the denoising away from the edges. This allows the filtering to remove noise in intermediate flat regions while respecting boundaries of objects better. The experimental results indicate that we can obtain improved video denoising results in comparison to other filtering methods.