SummaryThe objective of this study is to investigate the eff ects of irradiation from light-emitt ing diodes (LEDs) on several fruits during storage. To improve storage and increase the contents of some bioactive compounds, apple, tomato and red bell pepper fruits were exposed to yellow light emitt ed from the diodes at 590 nm. The contents of ascorbic acid, total phenolics, total fl avonoids and several pigments were investigated, along with the antioxidant potential. The colour parameters (L*, a* and b*) and fi rmness of the fruit were also determined. Aft er 7 days of LED light irradiation, there was signifi cantly higher total phenolic content and antioxidant potential in apple peel extracts. The irradiated fruit of tomato had signifi cantly higher levels of total phenolic compounds, and the fruit of red bell pepper had signifi cantly higher antioxidant potential. LED light had no eff ects on the colour parameters, although there was a tendency to accelerate colour development. Apple fruit irradiated with LED light was signifi cantly less fi rm. Among twelve analysed pigments, signifi cantly more β-carotene was detected in LED light-irradiated apple and bell pepper fruit, more α-tocopherol and γ-tocopherol in bell pepper fruit, and more lutein in apple peel and bell pepper fruit. The applied LED light slightly accelerated the ripening of the studied fruit, and aff ected the synthesis of some of the secondary metabolites.

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The paper describes a combined model of the highvoltage SF6 circuit breaker for digital simulations. The model is intended for detailed simulations of switching transients in electrical power systems in cases where interaction between physical phenomena in the circuit breaker and the system plays important role. The circuit breaker model is a black-box model introduced in the modeled system as a two-pole element with a variable impedance. The value of impedance is determined by a regulator dependent on a mathematical model. It consists of four partial models: a closed circuit-breaker model, a burning arc model, a current zero crossing model, and an open circuit breaker model. All four models are used in the same simulation sequence. The developed model can be used for various simulations as a one-phase model or as a three-phase model. In the paper, the model performance is verified and its practical applications are shown.

The improper illumination of cultural heritage buildings and monuments can be a source of enormous light pollution, which can have a major impact on the overall environment of the illuminated area. Such lighting can be the result of carelessness or a poorly designed lighting system. This paper presents one of the methodologies that can significantly reduce light pollution, especially spilt light out of building façades. The methodology is based on using luminaires with specially made shutters and an appropriate silhouette of the object. The shutters are designed with the help of photos of the object and the location’s sizes measured. The methodology was tested during the renovation of the lighting systems of different churches in Slovenia and is described using the example of the Church of St. Thomas near Ptuj, Slovenia (N46°28.9554′, E16°0.7416′). The results show that the methodology is effective and can significantly reduce light pollution that occurs when such buildings are incorrectly lit.

The aim of this paper is to present a complete analysis of the sky luminance distribution data measured with a sky scanner at the International Daylight Measurement Program station in Lyon. Besides presentation of the sky luminance distribution, we also derive the CIE sky type based on the CIE S 011/2003 standard. The CIE sky type is based on gradation and indicatrix functions. Determination of the gradation and indicatrix group is based on the calculation of luminance ratio between two elements on every almucantar. Since there are six gradation and six indicatrix groups, we have 36 combinations but only 15 of them are listed in the CIE standard. Since some of combinations are really rare, we provide a table to show how to allocate 36 combinations to 15 standard CIE sky types. At the end of the paper, we present frequencies of occurrence of CIE sky types in Lyon.