Papers by Keyword: Ripple

Abstract: High voltage DC power supply is very important in laser and high precision instruments, so the stability of high voltage DC power supply has an affect on the stability of laser and equipment. The voltage doubling rectifier circuit is the core component of the high voltage generator, so it is very important to study the stability of the voltage doubling rectifier circuit. Through the study of bidirectional rectifier circuit, double voltage rectifier circuit produces an output ripple and response time is superior than the basic voltage rectifier circuit. At the same time to study the bidirectional rectifier circuit is optimized, the capacity of the output arm greatly increases which leads to reduction in the output ripple, as the capacity reaches large enough value the output ripple approaches zero. Thus, greatly increasing the circuit in steady state time.

Abstract: In a single-phase photovoltaic grid connected system, the inherent second harmonic power flow results in large size impedance network of the Z-Source PV inverter. Minimization of the impedance network is a challenging area of research. So, a detailed mathematical approach based on 2ω ripple analysis is proposed. This paper depicts the 2ω modeling of Z-source inverter to obtain reduced component ratings of the impedance network. The analysis has been extended for Trans Quasi Z network and Embedded Z network and the component ratings are compared with Z network. Simulation has been carried out in MATLAB/Simulink for single phase Z-source PV inverter with impedance network designed using 2ω ripple analysis and the results are verified.

Abstract: In this paper, lapped C-face of single crystal SiC wafer was irradiated by femtosecond laser. Chemical mechanical polishing (CMP) was then carried out to polish the irradiated SiC C-face. The authors compared the results of femtosecond laser-assisted CMP process. A white-light interferometer was used to investigate the surface morphology of the processed SiC substrate before and after laser irradiation. It was found that the material removal rate (MRR) of the irradiated substrate is about 3 times higher than that of the substrate not treated by femtosecond laser. In addition, lower surface roughness was realized after femtosecond laser assisted CMP process.

Abstract: This essay is about the application of a diode-capacitor network on conventional non-isolated DC–DC converter. The study will focus on obtaining high step-up voltage gain, low switch voltage stress, simple control, and high conversion efficiency. Three single-switch step-up converters with high step-up ratio based on the diode-capacitor network are proposed. The principle of operation and theoretical analysis of every single-switch step-up converter is evaluated for both continuous and discontinuous conduction modes. Given the mirror-symmetrical characteristic of the diode-capacitor network, cascade single-switch step-up converters based on the single-switch positive-output step-up converter are achieved when several diode-capacitor networks are arranged in series. Simulation analysis and experimental results obtained from the implemented prototypes operating at 40 kHz are provided to verify the performances of the proposed step-up converters.

Abstract: Fuel cell is one of the promising renewable and sustainable power sources because of its high power density and very low emission. In order to design a highly efficient fuel cell power system, a suitable DC-DC converter is required. In this paper, a four-phase directly coupled Interleaved Boost Converter (IBC) for fuel cell is proposed. A four-phase structure with interleaved control is proposed to reduce the input current ripples, the output voltage ripples, and the size of passive components with high efficiency compared with the other topologies. Mathematical analysis of overall current ripple, design of inductance and other components is investigated. Simulation study of the proposed converter interfaced with fuel cells is carried out using MATLAB. A prototype is built using MOSFET to validate the simulation results.

Abstract: After introducing the design method of digital current (DC) power supply and the circuit schematic diagram and software flow chart of the key part, the paper designs the core processor based on ARM 32-bit Cortex™-M3 as controller, which, in hardware, has the features of high accuracy and simple circuit, and in function, parameters can be set both through keystroke and computer serial port. Meanwhile, the voltage and current of power supply are of high accuracy, quick in adjust response and with small output voltage ripple.

Abstract: Abstract: The polydimethylsiloxane (PDMS) film was applied a tensile strain, next the following steps was should be done: fixing the tensile strain, sputtering the gold film on the surface of PDMS film, and then releasing the tensile strain, a large-scale area ripple structure was formed. The ripple dislocations, the cracks and the oriented surface cracks appeared simultaneously during the forming of the ripple structure. This study also discussed the wavelengths of ripple structures resulted from the amount of tensile strain (30%, 50%, 70%, 90% and 110%) and gold thickness (4Å and 10Å). The wavelengths of ripple structures decreased as the tensile strains increased and gold thickness decreased.

Abstract: In this paper, we simulate by the particle-in-cell method (PIC) the mechanisms of femtoseconde (fs) laser interactions with a metallic or semiconductor target. Our aim is to identify the mechanisms that are responsible for surface nanostructure formation when laser fluences are close to the ablation threshold. For this purpose, we use a theoretical approach, which considers the solid as a gas of free electrons in a lattice of immobile ions. As a result, the simulations shown that those nanostructures occur during the first moments of the interaction and are due to the inhomogeneous distribution of the density of the electrons

Abstract: With femtosecond laser pulse (130 fs, 800 nm, 1 kHz pulse repetition frequency) irradiation on Au/Cr film stack, several nanostructures were obtained. The influence of laser parameters such as fluence(0.5J/cm2,2J/cm2) and the number of pulse were investigate. With single pulse irradiation, the nanoline and periodic ripple structures were obtained for the pulse fluence of 0.5J/cm2 and 2J/cm2, respectively. The formation mechanism of those nanostructures were discussed.

Abstract: We carried out cross-sectional transmission electron microscopy (TEM) investigation of femtosecond laser-induced ripples formed on 4H-SiC single crystal surface. Here, we paid attention to the crystal structures underlying the coarse and fine ripples and the three-dimensional distribution of amorphous phase. Conventional and high-resolution TEM analyses made clear that a continuous amorphous layer approximately of 50 nm thick exist at the topmost region of both coarse and fine ripples. The result strongly suggests that the fundamental surface deformation process is common for coarse and fine ripples, even though the factors which determine their periods are different.