The oral hygiene regimens in Germany and Poland were not comparable, as more plaque was found in the Polish than in the German population. Plaque accumulation seems not to be a key factor in causing periodontal destruction in the cleft area. Factors other than oral hygiene should be considered of major importance in relation to the development of gingival recession on teeth in cleft areas.

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The presented paper is part of the complete description of fluid‐dynamic conditions in the selected static mixers: Koflo and Kenics. The research was also performed for an empty pipe used as a reference state. The scope of work included the analysis of the residence time distribution in the mentioned devices for different Reynolds numbers for both laminar and turbulent flow regimes. The report contains a discussion about residence time distribution function E(t), cumulative distribution function F(t), as well as the parameters like the mean residence time tm and the variance σ2. The main aim of the presented work was to show the applicability of static mixers as chemical reactors and to present their operation characteristics to evaluate the derogations distinguishing them from well known ideal states (i.e. plug flow or ideal mixing). As a result of the accomplished study it was proved that Reynolds number increase results in narrower RTD in all of the tested devices, however the fluid motion is far from plug flow due to axial and radial mixing and the considered equipment should be treated as non‐ideal reactors requiring some additional models for the right description. What is more, in the case of laminar flow, the Kenics static mixer showed the narrowest spread and was considered as the best solution among the studied devices. In the turbulent flow, the difference between E(t) functions for all of the mentioned equipment was so small that the suggestion of small impact of insert type on the RTD was made.

A new method, named as the nested k‐means, for detecting a person captured in aerial images acquired by an unmanned aerial vehicle (UAV), is presented. The nested k‐means method is used in a newly built system that supports search and rescue (SAR) activities through processing of aerial photographs taken in visible light spectra (red‐green‐blue channels, RGB). First, the k‐means classification is utilized to identify clusters of colors in a three‐dimensional space (RGB). Second, the k‐means method is used to verify if the automatically selected class of colors is concurrently spatially clustered in a two‐dimensional space (easting‐northing, EN), and has human‐size area. The UAV images were acquired during the field campaign carried out in the Izerskie Mountains (SW Poland). The experiment aimed to observe several persons using an RGB camera, in spring and winter, during various periods of day, in uncovered terrain and sparse forest. It was found that the nested k‐means method has a considerable potential for detecting a person lost in the wilderness and allows to reduce area to be searched to 4.4 and 7.3% in spring and winter, respectively. In winter, land cover influences the performance of the nested k‐means method, with better skills in sparse forest than in the uncovered terrain. In spring, such a relationship does not hold. The nested k‐means method may provide the SAR teams with a tool for near real‐time detection of a person and, as a consequence, to reduce search area to approximately 0.5–7.3% of total terrain to be visited, depending on season and land cover.

In the process industry the use of static mixers is constantly rising. Notwithstanding, due to the multitude of available types, the selection of a proper construction is not as simple and requires the knowledge of complete description of a device. In the performed research there was an attempt to present the complete fluid‐dynamic characteristics of two static mixers: Kenics, well known and commonly used, and Koflo, which has not yet been described in the relevant literature. The empty pipe was also studied as a background for comparison. However, according to the huge amount of gathered data, the report was divided into separate parts, dedicated to pressure drops, residence time distributions, and mixture homogeneity, respectively. The presented paper is focused on the pressure drop analysis which contains the experimental study, the validation of the obtained data on the basis of manufacturer's correlations, as well as computational values and the presentation of new pressure drop relations that enable the pressure drop predictions from Eu or Ne number. As a result of the accomplished study, a good accuracy between the values calculated form given equations and those achieved in the experimental manner was confirmed. It was also shown that due to smaller energy consumption Koflo static mixer can be successfully used instead of Kenics. What is more, the presented report clearly states that static mixers require a huge power demand which leads to the increased maintenance costs and that information should be considered during the system design.