32 research outputs found

    Comparison between Intravitreal Injection of Ranibizumab and Bevacizumab as Preoperative Measure for Diabetic Vitrectomy

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    Purpose: In order to examine the parameters of surgical operation between intravitreal bevacizumab and ranibizumab as adjuvant therapy before pars plana vitrectomy in proliferative diabetic retinopathy. Patients & methods:A randomized clinical study on 68 eyes, the patients are classified into two groups, group A (n = 34), and group B (n =34), both groups injected by anti-vascular endothelial growth factor before vitrectomy operation, group A injected by Bevacizumab and group B injected by Ranibizumab, the duration between injection and the operation was 3-6 days, the basic data of each patient include vision, type of DM, duration of DM, level of HbA1c, during the operation we record the following parameters diathermy application number, breaks, bleeding, bottle height, and type of tamponade. Results: The mean BCVA was improved from base line to post- operative in both groups without statistically difference between the groups p value =0.231, diathermy application was one application in 30.3% in group A and 32.4% in group B, and two applications in 15.2% in group A and 2.9% in group B. break was one break in 23.5% in group A and 20.6% in group B. two breaks in 2.9% in each group. Bleeding was in 16 cases in group A and 17 cases in group B. tamponade was silicon in 58.8% in group A and 52.9% in group B, fluid tamponade was 38.3% in group A and 44.2% in group B, air tamponade was one case in each group. without statistical difference between groups. Conclusion: When administered preoperatively during a diabetic vitrectomy procedure, there is no difference between bevacizumab and ranibizumab

    A vector control strategy for five-phase drives fed by simplified split-source inverters

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    A vector control strategy for five-phase drives fed by simplified split-source inverters

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    Modeling and control of stand-alone photovoltaic system based on split-source inverter

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    Symmetrical nine-phase drives with a single neutral-point: common-mode voltage analysis and reduction

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    Power converters generate switching common mode voltage (CMV) through the pulse width modulation (PWM). Several problems occur in the drive systems due to the generated CMV. These problems can be dangerous to the insulation and bearings of the electric machine windings. In recent years, many modulation methods have been developed to reduce the CMV in multiphase machines. Symmetrical nine-phase machines with single-neutral are considered in this paper. In this case, conventional PWM uses eight active vectors of different magnitudes in combination with two zero states in a switching cycle, and this generates maximum CMV. This paper proposes two PWM schemes to reduce the CMV in such a system. The first scheme is called active zero state (AZS). It replaces the zero vectors with suitable opposite active vectors. The second scheme uses ten large active vectors during switching and is called SVM-10L. Compared with conventional strategies, the AZS reduces the peak CMV by 22.2%, and the SVM-10L reduces the peak CMV by 88.8%. Moreover, this paper presents a carrier-based implementation of the proposed schemes to simplify the implementation. The proposed schemes are assessed using simulations and experimental studies for an induction motor load under different case studies

    Modeling and control of single-stage quadratic-boost split source inverters

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    This paper aims to develop the recently introduced Spilt-Source Inverter (SSI) topology to improve its boosting characteristics. New SSI topologies with high voltage gain are introduced in this paper. The proposed converters square the basic SSI’s boosting factor by utilizing an additional inductor, capacitor, and two diodes. Thus, the proposed converters are called Quadratic-Boost (or Square-Boost) SSIs (QBIs or SBIs). Four different QBI topologies are presented. One with continuous input current (CC-QBI), and the other draws a discontinuous input current (DC-QBI) but with reduced capacitor voltage stresses. This paper also introduces the small-signal model of the CC-QBI using state variables perturbance. Based on this model, the closed-loop voltage and current control approach of the dc-boosting factor are designed. Moreover, a modified space vector modulation (MSVM) scheme is presented to reduce the input current ripples. To evaluate the performance of the proposed topologies, a comparative study between them and the other counterpart from different perspectives is introduced. It can be found that the CC-QBI topology has superior boosting characteristics when operating with low input voltage compared with their counterparts. It has a higher boosting capability, lower capacitor voltages, and semiconductor stresses, especially when high voltage gains are required. These merits make the proposed topologies convenient to the Photovoltaic and Fuel-Cell systems. Finally, the feasibility of the suggested topology and the introduced mathematical model is verified via simulation and experimental results, which show good accordance with the theoretical analysis. AuthorScopu

    Performance of a six-phase induction motor fed from a Z-source inverter under faulty conditions

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