Analytic models for a bidirectional coupled-inductoŕ Cuk converter operating in sliding mode are described. Using a linear combination of the converter four state variable errors as a general switching surface, the expression for the equivalent control is derived and the coordinates of the equilibrium point are obtained. Particular cases of the general switching surface are subsequently analyzed in detail: 1) surfaces for ideal line regulation, 2) surfaces for ideal load regulation, and 3) surfaces for hysteretic current control. Simulation results verifying the analytical predictions are presented.

The objective of this paper is to analyse occupational mobility among immigrants in Spain in two distinct stages: (1) comparing the immigrants' first job in Spain with their profession in the country of origin and (2) comparing their current occupational status with the occupational status of the first job they held in Spain. We focus on immigrants who arrived in Spain during the ''immigration boom'' that took place between 1997 and 2007, using data from the 2007 National Survey on Immigration. For our analysis, we use occupational mobility tables and multi-variable models with occupational mobility as a dependent variable. Our results show that we can better understand the initial access of migrants to the Spanish labour market from the perspective of labour market segregation: for each gender, a particular sector/occupational level (construction and cleaning, respectively) played such a dominant role that it determined almost entirely the observed mobility pattern. We find some (upward) mobility opportunities after such initial strong segregation, which increased with length of residence; however, our results suggest that, even in this case, it is mostly limited to men and associated with the construction boom that finished abruptly in 2007.

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Abstract-This paper is devoted to the design of a sliding-mode control scheme for a buck-based inverter, with programmable amplitude, frequency, and dc offset, with no external sinusoidal reference required. A general procedure for obtaining an autonomous (time independent) switching surface from a time-dependent one is presented. For this surface, the system exhibits a zeroth-order dynamics in sliding motion. On the other hand, from the sliding-domain analysis, a set of design restrictions is established in terms of the inverter output filter Bode diagram and the output signal parameters (amplitude, frequency and dc offset), facilitating the subsequent design procedure. The control scheme is robust with respect to both power-stage parameter variations and external disturbances and can be implemented by means of conventional electronic circuitry. Simulations and experimental results for both reactive and nonlinear loads are presented.

Under conditions of order reduction, a nonlinear control of a bidirectional coupled-inductor Cuk converter suitable for large-signal applications is presented. The converter is accurately modeled as a second-order bilinear system and the conditions established for local controllability. The integration of converter state equations and the subsequent introduction of a linear recurrence between the output variable and an external reference signal lead to a nonlinear control law that is implemented by means of an analog divider, standard operational amplifiers, and a pulse-width modulator. As a result, the output variable follows proportionally the reference signal, this allowing the obtention of different types of power waveforms in the converter output. Experimental results verify the theoretical predictions.