Composite panels are widely used as structural members due to their high strength-to-weight ratio. In order to reduce further weight, cutouts or notches are introduced in these members. These cutouts also serve utility requirements such as man-holes for purpose of service as well as for passing electric or fuel lines. An aircraft wing rib is a typical example of such a composite panel. Even while composites with holes or cutouts provide great savings in weight compared to metallic structures, the presence of holes itself leads to strength reduction. The reduction in strength is due to the concentration of stress around the vicinity of the hole while the structure is under loading. Different-sized and shaped holes/cut-outs are used in composites structural members, which may serve for different purposes. They, in turn, introduce their own versions of stress concentrations effects in such members leading to weakening of the structure. The stress concentration effect in fibre composites also depends on other factors like fibre orientation, fibre material, matrix material, etc. Loading can also influence stress concentration. This review pursues vast research done in this area and attempts to compare and summarise the diverse findings for designers to obtain a comprehensive concept on stress concentration factor as an effective tool for composite structure design.
This paper compares the reduction of harmonics in various level cascaded H-bridge inverters. The switching angles for the cascaded H-bridge inverter were calculated by evolutionary optimization technique. Fourier analysis is used to determine the switching angles for the desired electrical parameters. Lower order harmonics such as third, fifth, seventh, ninth and eleventh order harmonics were taken into consideration to reduce the total harmonic distortion. Simulation was done for thirteen, fifteen and seventeen level cascaded H-bridge inverters using Matlab. Total harmonic distortion of voltage and current for R, RL and Motor load were analyzed.
A high gain nonisolated DC-DC converter using a single power semiconductor switch is proposed in this article. The operation of the proposed converter is explained under continuous conduction mode (CCM), discontinuous conduction mode (DCM), and boundary conduction mode (BCM). The mathematical expressions for steady-state voltage gain, voltage stress, and current stress of diodes and switch are provided. Also, the design of inductors and capacitors in the CCM mode is explained with appropriate mathematical equations. The proposed topology is tested with a 200 W prototype at 50 kHz and a 60% duty cycle. The dynamic behavior of the proposed converter is examined by changing the duty cycle value and also load values. The proposed converter is verified with experimental results to prove the effectiveness of its operation. The proposed converter provides higher steady-state voltage gain as compared with recently developed topologies. The efficiency and power density of the proposed converter is 90% and 1.16 kW/L, respectively.
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