Effect of a finite r.f. conductance of native oxide on InP metal/insulator/semiconductor admittance

Metal/insulator/semiconductor capacitors were fabricated on n-type InP by growing a native thin double-layer insulator film in an oxygen plasma. Such structures greatly improve the interface properties compared with those of insulators prepared with a conventional single-layer oxide, but the resistivity of the film remains quite unchanged with typical values of 10⁹ Ω cm. Electrical analysis of the data show that (i) some anomalous frequency dispersion is observed in the capacitance-voltage characteristics when the semiconductor is brought into accumulation and (ii) the conductance-voltage curves do not show any peak in the positive bias range. To explain the frequency dispersion, a model was developed which incorporates the losses in the oxide. Taking into account the parallel conductance of the insulator, the anomalous behaviour observed in the positive bias range is then suppressed and the correlated high and low frequency capacitance-voltage curves are in agreement with the theoretical curves.     

An Embedded Solar‐Powered Irrigation System Based on a Cascaded Fuzzy Logic Controller

This study examines the automatization of irrigation tasks of solar photovoltaic water pumping systems (SPVWPS) in greenhouse applications. A prototype of an embedded control system has been developed for SPVWPS battery‐coupled architectures. The new design aims at improving the safety of solar irrigation facility by avoiding the exhaustion of pumping resources (water and energy) while watering. The availabilities of pumping resources are introduced as new requisite inputs of a fuzzy logic‐based control system (FLC) so that it can produce adequate and safe irrigation durations. The FLC design consists of two cascaded devices. The first device uses climate data to estimate durations for watering that satisfy crop needs. The second device uses actual resource levels to evaluate the pumping capacity of the SPVWPS regarding requested durations. Watering is performed whenever the pumping capacity of the system represents more than 25% of the total requirement. Test results from an experimental greenhouse prove the effectiveness of the decision‐making mechanism that prevents scheduling unsuccessful watering tasks.     

Linear analysis of mechanics of single and multiple cracks at fiber/matrix interface using axisymmetric model

It is well known that the life of material composite depends on the hardness of the interface between the fiber and the matrix. Herein, the aim of this work is the calculation by finite element method interaction effect between a crack and an interface by energy release rate approach. The first part of this work is devoted to the crack normal to the interface and the second one deals with the crack terminated at the interface. In this study, two cases are considered using a copper matrix with different fibers. An axisymmetric model has been used to evaluate the conditions for the crack deflection/penetration by the interface as well as the effects of the volume percent of fibers and the effects of the distance between the crack tip and the interface were highlighted as well as the effects of the elastic properties of two bonded materials.