Nowadays microinverter with power levels ranging from 150 to 300 W, has become the trend for some grid-connected PV systems specially for residential PV systems. Also, in marine industries, photovoltaic microinverters can be used to produce a part of the electrical energy required on ships. In single phase microinverters there is a double-frequency ripple on the DC bus voltage that causes harmonics and reduces power factor. In order to reduce this ripple, large electrolytic capacitors are often used at the DC bus that the drawback is short lifetime of these capacitors. To overcome this problem, it is necessary to replace electrolytic capacitors with thin film capacitors that have long life and LOW capacitance. By decreasing the capacitance the amplitude of double frequency ripple on the bus voltage increases so the common bus voltage controller (PI) can’ t solve the tradeoff between the output current THD and bus voltage fluctuations (overshoot and undershoot). In this paper, by using the proposed control methods a microinverter is designed and simulated so that this tradeoff has been solved without using additional hardware. This microinverter is connected to the grid (220V, 50Hz). It has a very small 20µ F bus capacitor. The bus voltage has negligible overshoot and undershoot in response to a 200W input power step. THD of the injected current to the grid is 0. 44% at 250W output power. The effectiveness of the proposed method is validated by simulation results in Matlab-Simulink software.

This paper investigates a fundamental issue in AC-DC rectifiers that are specifically used as charger for electric vehicle (EV), i. e. the total harmonic distortion (THD) of input current waveforms. Firstly, the topology of two-stage charger along with the corresponding control scheme is reviewed. Then, the research gap namely high harmonic distortion of input current is identified and analyzed. A revision of the conventional control method with the aid of virtual resistant is proposed and investigated from the circuit perspectives. Finally, simulation results are delivered to validate the analysis and the reduction of THD in the input current waveform. this is proposed method, the steady state is studied.

The multilevel cascade inverter is one of the most widely used power-electronics based interfaces in electrical distribution systems. Due to high losses and harmonics, the switching frequency of the inverter should be LOW in medium and high power applications. For this reason, the conventional carrier wave-based sinusoidal pulse modulation (PWM) and space vector PWM that have high switching frequencies cannot be used in these applications. The optimal PWM methods for inverters with step modulation result in LOWer total harmonic distortion (THD) in output voltage than other common modulation methods. However, one of the major disadvantages of these methods is that the optimal switching angles should be determined using the switching table, limiting the application of the optimal PWM. This paper proposes a method for determination of switching angles by using the iterative quadratic programming method. In each iteration, the proposed method calculates the switching angles by solving the quadratic sub equations with equality constraints and linear equations. Also in the appropriate conditions, global and asymmetric convergences are faster, more accurate, and more efficient, and there is no need for much time and memory for switching angles determination. The optimum switching angles minimize the switching frequency, switching losses, and THD in voltage and current of a three-phase cascade multilevel inverter with step modulation. Also, the power circuit breakers are switched on and off only once in each period. The effectiveness of the proposed method is evaluated through simulation case studies in MATLAB environment.

Background and Aim: Salivary gland tumors classification continuously undergoes alternations, especially in the recent years. This study used immunohistochemical markers for distinguishing between polymorphous LOW-grade adenocarcinoma (PLGA) and adenocarcinoma carcinoma (AdCC) which have several overlapping histological and clinical features.Materials & Methods: Ten AdCC and eight PLGA with five normal minor salivary glands were selected after review by two oral pathologists.  LSAB method was used for seven markers: carcinoembryonic antigen, epithelial membrane antigen, muscle specific actin, vimentin, S100, P53 and Ki-67. Finally, the data were analyzed by Mann-Whiteny test.Results: Analysis of data showed a high expression of CEA, EMA and Ki-67 in AdCC compared to PLGA. Although, CEA (P Less than 0.001) expression was limited to luminal cells .In contrast, MSA (P=0.034) expression in nonluminal cells, and Ki-67 (P Less than0.001) occurred in both luminal and nonluminal cells. Also there was highly expression of vimentin and S-100 in PLGA with no significancy for EMA and Tp53. Conclusion: The result of this study suggests that ICH can be a helpful tool. The immunostaining of AdCC and PLGA with CEA, Vimentin and Ki-67 were of greater significant, S100 and MSA were less significant and the others (EMA and P53) could not offer an adjunctive aid in differential diagnosis between the two tumors. 

Background and Aims: Lasers with different characteristics have been used to stimulate orthodontic tooth movement. Considering the contradictory findings in this regard, this study was designed to assess the effect of LOW level laser therapy (LLLT) on the rate of orthodontic tooth movement.Materials and Methods: In this randomized clinical trial study, 12 patients (4 boys and 8 girls; average age: 16.9±3.4) with extracted upper first premolars and required canine retraction into extraction site were included. While in both sides canines were retracted by NiTi coil spring, one side was exposed to GaAlAs laser (890 nm). LLLT was done (on the buccal and palatal mucosa by sLOW movement of probe) at the beginning of the first month. Impression and cast fabrication performed at the beginning of retraction, one and two months later. The amount of retraction on the cast was measured with the aid of a reference plaque fabricated on the rogae using a digital caliper. Data were analyzed using paired sample T-test and one-sample Kolmogorov-Simirnov test.Results: There was no significant difference in the amounts of canine movement between laser exposed and control sides (P>0.05).Conclusion: The energy dose of laser used in this study (72 J per each tooth) was not appropriate for increasing dental movement.

Multilevel voltage source inverters have several advantages compare to traditional voltage source inverter. These inverters reduce cost, get better voltage waveform and decrease Total Harmonic Distortion (THD) by increasing the levels of output voltage.In this paper Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) methods are used to find the switching angles for achieving to the minimum THD for output voltage waveform of the Cascaded H-bridge Multi-Level Inverters (MLI). These methods are used for a 27-level inverter for different modulation indices. Result of two methods is identical and in comparison to other methods have the smallest THD. To verify results of two mentioned methods, a simulation using MATLAB/Simulink software is presented.

Background: Considering the importance of removal of these solutes in chronic renal failure patients, this study was carried out to evaluate the effect of increasing ultrafiltration on clearance of middle molecules in LOW-flux hemodialysis in Kashan, 2005.Materials and Methods: Twenty one hemodialysis patients, 11 women and 10 men, were enrolled to this clinical before-after study. At the first stage the patients were dialyzed with ultrafiltration equal to their dry body weight. At the second stage two liters was added to the ultrafiltration and clearance of each solute was calculated in both stages. Data were analyzed using SPSS software and square T test.Results: There was a significant difference in clearance of b2-microglobulin and vitamin B12 in second stage in comparison with the first one (p<0.03, p<0.001), respectively. While there was no difference in clearance of small molecules P, BUN, and Cr. (p=0.97, r=0.24, p=0.36). In first hemodialysis KT/V was 1.12 and in the second 1.22. Conclusion: It was shown that in LOW-flux hemodialysis the increase in ultrafiltration results in increased clearance of middle molecules. Ultrfiltration increase also improves the adequacy of hemodialysis but it doesn't affect removal of small molecule.