Quasi-normal-eigenvalue optimization is studied under constraints b 1 (x) ≤ B(x) ≤ b 2 (x) on structure functions B of 2-side open optical or mechanical resonators. We prove existence of various optimizers and provide an example when different structures generate the same optimal quasi-(normal-)eigenvalue. To show that quasi-eigenvalues locally optimal in various senses are in the spectrum Σ nl of the bang-bang eigenproblem yis the indicator function of C + , we obtain a variational characterization of Σ nl in terms of quasi-eigenvalue perturbations. To address the minimization of the decay rate | Im ω|, we study the bang-bang equation and explain how it excludes an unknown optimal B from the optimization process. Computing one of minimal decay structures for 1-side open settings, we show that it resembles gradually size-modulated 1-D stack cavities introduced recently in Optical Engineering. In 2-side open symmetric settings, our example has an additional centered defect. Nonexistence of global decay rate minimizers is discussed. MSC-classes: 49R05,

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The paper deals with a power charger capable of quick simultaneous charging of several unevenly discharged batteries. The charger is designed for use in conjunction with a recently developed power-assist wheelchair composed of two armrest modules associated with wheels—each with its own motor, driver and battery. Uneven discharge of the batteries is very possible in this application. Taking into account the charging power and energy comparable with the most powerful household electrical devices, the refreshing of these batteries and integration of the entire power supply chain into the household grid become a topical and challenging task. Solving of this task requires a special charger that has several channels and can unevenly apply charging power to these channels. At the same time, the charger must not generate current harmonics or reactive power, must operate with good efficiency and satisfy size constraints. In the given research, a configuration of several interleaved isolated single-ended primary-inductor converters is studied. The synthesized mathematical model of the proposed charger provides data about its static and dynamic characteristics while its experimental investigation focuses on operation details (power losses, control features etc.). The obtained results prove that the proposed concept complies with the above-mentioned requirements and can be applied in the discussed application.

-The study is devoted to the important issue of enhancing the circuitry and characteristics of power supplies for micro resistance welding machines. The aim of the research is to provide high quality input current and to increase the energy efficiency of the output pulse generator by means of improving the circuit topologies of the power supply main blocks. In study, the principle of constructing the power supply for micro resistance welding, which provides high values of output welding current and high accuracy of welding pulse formation, makes it possible to reduce energy losses, and provides high quality of consumed input current, is represented. The multiphase topology of the charger with power factor correction based on SEPIC converters is suggested as the most efficient for charging the supercapacitor storage module. The multicell topology of the supercapacitor energy storage with voltage equalizing is presented. The parameters of the converter cells are evaluated. The calculations of energy efficiency of the power supply's input and output converters based on suggested topologies are carried out and verified in MATLAB Simulink. The power factor value greater than 99 % is derived.

Rapid developments in energy storage and conversion technologies have led to the proliferation of low-and medium-power electric vehicles. Their regular operation typically requires an on-board battery charger that features small dimensions, high efficiency and power quality. This paper analyses an interleaved step-down single-ended primary-inductor converter (SEPIC) operating in the discontinuous conduction mode (DCM) for charging of battery-powered light electric vehicles such as an electric wheelchair. The required characteristics are achieved thanks to favourable arrangement of the inductors in the circuit: the input inductor is used for power factor correction (PFC) without additional elements, while the other inductor is used to provide galvanic isolation and required voltage conversion ratio. A modular interleaved structure of the converter helps to implement low-profile converter design with standard components, distribute the power losses and improve the performance. An optimal number of converter cells was estimated. The converter uses a simple control algorithm for constant current and constant voltage charging modes. To reduce the energy losses, synchronous rectification along with a common regenerative snubber circuit was implemented. The proposed charger concept was verified with a developed 230 VAC to 29.4 VDC experimental prototype that has proved its effectiveness.