The paper describes issues related to pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger’s plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 μm, 571 μm, 750 μm, and 823 μm. In addition, more complex geometry has been investigated, equipped with additional diagonal channels (so called extended geometry). The moment of the liquid phase transition through the heat exchanger was recorded at the flow rates ranging from 0.83 g/s to 13.33 g/s in the inlet manifold. The paper discusses the total pressure drop as a function of the flow rate and the characteristic dimension of minichannels, as well as the pressure drop as a function of the time of the fluid passage through the main part of the measuring section in which measurements were done. The resulting profiles correlate with the images of the flow distribution between channels recorded using the fast shutter speed camera, that allows to draw a further conclusions about the specifics of the maldistribution process. The impact of the total pressure drop on the actual range of optimum operating conditions of the heat exchanger was analyzed.

Analysis of the state of-the-art in research of minichannel heat exchangers, especially on the topic of flow maldistribution in multiple channels, has been accomplished. Studies on minichannel plate heat exchanger with 51 parallel minichannels with four hydraulic diameters, i.e., 461 μm, 574 μm, 667 μm, and 750 μm have been presented. Flow at the instance of filling the microchannel with water at low flow rates has been visualized. The pressure drop characteristics for single minichannel plate have been presented along with the channels blockage, which occurred in several cases. The impact of the mass flow rate and channels’ cross-section dimensions on the flow maldistribution were illustrated.

The article presents an analysis of the real role of the complementarity principle and the reasons why immi-gration law is still based on this principle. The basic assumptions of the state’s attitude towards labour im-migration were set out in a period when this kind of immigration to Poland was at a much smaller scale than currently. First and foremost, one of the basic premises is the complementarity of labour immigration (com-plementarity principle) with the labour market test as an element of the procedures, although with some exceptions. The mechanism of controlling the complementarity is obligatory and preventive. The current economic situation in Poland, including the conditions for the functioning of immigration law, is very differ-ent from the reality of that time. In view of growing shortages of Polish employees on the labour market one can doubt whether preventive enforcement of complementarity by law is needed. The complementarity of labour immigration to Poland is a socio-economic fact and legal guarantees to ensure this result seem ob-solete. There are strong arguments to consider that opportunistic political motivations are the main reason against the rationalisation of legal regulations concerning immigration of workers. The complementarity principle has become a facade of restrictive immigration law, while allowing for its use in a way that ensures the access of immigrants to the labour market.

The article discusses the applicability of a novel method to determine horizontal curvature of the railway track axis based on results of mobile satellite measurements. The method is based on inclination angle changes of a moving chord in the Cartesian coordinate system. In the presented case, the variant referred to as the method of two virtual chords is applied. It consists in maneuvering with only one GNSS (Global Navigation Satellite System) receiver. The assumptions of the novel method are formulated, and an assessment of its application in the performed campaign of mobile satellite measurements is presented. The shape of the measured railway axis is shown in the national spatial reference system PL-2000, and the speed of the measuring trolley during measurement is calculated based on the recorded coordinates. It has been observed that over the test section, the curvature ordinates differ from the expected waveform, which can be caused by disturbances of the measuring trolley trajectory. However, this problem can easily be overcome by filtering the measured track axis ordinates to obtain the correct shape – this refers to all track segments: straight sections, circular arcs and transition curves. The virtual chord method can also constitute the basis for assessing the quality of the recorded satellite signal. The performed analysis has shown high accuracy of the measuring process.

A graphene/NPB structure with Re₂O₇ as an interfacial layer in the context of its potential use in the design of an organic light-emitting diode (OLED) is investigated. The X-ray photoelectron spectroscopy (XPS) study shows the formation of the Re₂O₇ phase on a monolayer graphene on quartz during thermal deposition in ultra-high vacuum (UHV). The ultraviolet photoelectron spectroscopy (UPS) study shows an enhancement of the work function of the graphene heterostructure after deposition of the Re₂O₇ layer up to 5.4 eV. The hole injection barrier between the Re₂O₇/graphene heterostructure and the N-bis-(1-naphthyl)-N,N-diphenyl-(1,1-biphenyl)-4,4-diamine (NPB) layer was estimated to be 0.35 eV, which is very promising for a good OLED performance.

The presented research shows that commercially available graphene on quartz modified with rhenium oxide meets the requirements for its use as a conductive and transparent anode in optoelectronic devices. The cluster growth of rhenium oxide enables an increase in the work function of graphene by 1.3 eV up to 5.2 eV, which guarantees an appropriate adjustment to the energy levels of organic semiconductors used in organic light-emitting diode devices.