Three-Phase Multistage System (DC-AC-DC-AC) for Connecting Solar Cells to the Grid

Inverter systems that feed electrical power from photovoltaic (PV) system into the grid must convert the direct current of the PV array into the alternating current of the grid. In many applications, it is important for a converter to be lightweight, highly reliable, input/output isolated, flexible and operable in a boost mode. These features can be achieved by using a High-Frequency inverter which involves an isolated DC-DC stage and DC-AC section, which provides AC output. This paper proposes a new three phase topology, based on multi stage converter and PV system in order to use in medium and high power applications. The Perturb and Observe (P&O) method is used for maximum power point tracking (MPPT) control of PV array. The switching control signals for three-phase inverter are provided by hysteresis control method. Also, the comparison between the proposed topology and traditional structures has been conducted and finally the simulation researches are performed in a closed-loop control system by MATLAB/Simulink software to verify the operation of the proposed structure. The results represent better performance of the introduced system over traditional topologies

Drug-drug interactions in prescriptions of Lorestan province, Western of Iran

Rational prescribing means prescribing the more effective and healthiest drug for a disease according to patient’s condition, the type of effective drugs, cost and etc. The non-normative and non-rational prescribing of medicine can cause side effects. Prescribing of effective and safe drugs can have an important role in treatment of patient and the lack of side effect, drug interactions and imposition of additional cost. The aim of this study was to evaluate drug interactions in prescriptions of Lorestan province, western of Iran In this study, at first, the statistic of the insurance prescription of all provincial pharmacies were obtained, interred in the prescription review software of food and drug administration, processed in terms of drug interactions and data were statistically analyzed. This study shows that of the total 1443973 of the prescription numbers, 1112 numbers of that contain 1.25 mg of Digoxin tablets with 40 mg of Furosemide tablets that they have a severe interaction and can lead to arrhythmia in patients. Also 934 prescriptions contain Gemfibrozil and Lovastatin which can lead to myopathy and rhabdomyolysis in consumer patients. The survey revealed that 1.36, 3.76 and 0.56% of prescriptions have mild, moderate and severe interactions, respectively. Existence of severe and moderate drug interactions requires that further workshops be held for physicians on drug interactions

Individual effect of recrystallisation nucleation sites on texture weakening in a magnesium alloy: Part 1- double twins

Recrystallised grain nucleation, grain growth and corresponding texture evolution in a cold-rolled rare earth containing WE43 Mg alloy during annealing at 490 �C was fully tracked using a quasi-in-situ electron backscatter diffraction method. The results show nucleation sites, such as double twins, can weaken the deformed texture and for the first time provide direct evidence that recrystallised grains originating from double twins can form the rare earth texture during annealing. Precipitation and recrystallisation occurred concurrently during most of the annealing period, with precipitates forming preferentially along prior grain and twin boundaries. These precipitates effectively retard the recrystallisation due to particle pinning leading to an excessively long time for the completion of recrystallisation. A large portion of recrystallised grains were observed to have 〈0001〉 poles tilted 20e45� away from the normal direction. The RE texture emerges during the nucleation of recrystallised grains and is maintained during subsequent uniform grain growth, which results in a stable RE texture being developed as recrystallisation progresses. The uniform grain growth could be attributed to solute drag suppressing the grain boundary mobility of those grains that had recrystallised with a basal texture and precipitate pinning restricting potential orientated grain growth

Vibration-based cavitation detection in centrifugal pumps

Cavitation is a common cause of failure in centrifugal pumps. Because of interaction of several mechanical parts and fluid, the vibration signal of a centrifugal pump is complicated. In this paper, the vibrations of a transparent-casing centrifugal pump are studied. Three states are studied experimentally: no cavitation, limited cavitation and developed cavitation. Each case was also confirmed by visually inspecting the cavitation bubbles. The vibrations of the pump was acquired by using an accelerometer that was attached to the casing. Discrete wavelet transform (DWT) analysis and empirical mode decomposition (EMD) are used to extract classification features from the acquired signals. Using these features, an artificial neural network (ANN) successfully diagnosed the cavitation condition of the pump. Finally, EEMD is also implemented. The results showed the success of EMD and DWT in cavitation diagnosis. The output of EEMD does not show significant change comparing to EMD