This paper presents the design process and the results of a novel fall detector designed and constructed at the Faculty of Electronics, Military University of Technology. High sensitivity and low false alarm rates were achieved by using four independent sensors of varying physical quantities and sophisticated methods of signal processing and data mining. The manuscript discusses the study background, hardware development, alternative algorithms used for the sensor data processing and fusion for identification of the most efficient solution and the final results from testing the Android application on smartphone. The test was performed in four 6-h sessions (two sessions with female participants at the age of 28 years, one session with male participants aged 28 years and one involving a man at the age of 49 years) and showed correct detection of all 40 simulated falls with only three false alarms. Our results confirmed the sensitivity of the proposed algorithm to be 100% with a nominal false alarm rate (one false alarm per 8 h).

The paper presents results of the field tests on membrane biogas enrichment performed with the application of mobile membrane installation (MMI) with the feed stream up to 10 Nm3/h. The mobile installation equipped with four hollow fibre modules with polyimide type membranes was tested at four different biogas plants. Two of them were using agricultural substrates. The third one was constructed at a municipal wastewater plant and sludge was fermented in a digester and finally in the fourth case biogas was extracted from municipal waste landfill site. Differences in the concentration of bio-methane in feed in all cases were observed and trace compounds were detected as well. High selectivity polyimide membranes, in proper module arrangements, can provide a product of high methane content in all cases. The content of other trace compounds, such as hydrogen sulphide, water vapour and oxygen on the product did not exceed the values stated by standard for a biogas as a vehicle fuel. The traces of hydrogen sulphide and water vapour penetrated faster to the waste stream enriched in carbon dioxide, which could lead to further purification of the product – methane being hold in the retentate (H2O > H2S > CO2 > O2 > CH4 > N2). In the investigated cases, when concentration of N2 was low and concentration of CH4 higher than 50%, it was possible to upgrade methane to concentration above 90% in a two-stage cascade.

To performsimulation ofCH4 andCO2 permeation through polyimide membrane,MATLABwas used. Simulation program has included permeation gaseous mixture with methane contents as observed at field tests in the range of 50 and 60% vol. The mass transport process was estimated for a concurrent hollow fibre membrane module for given pressure and temperature conditions and different values of stage cut. The obtained results show good agreement with the experimental data. The highest degree of methane recovery was obtained with gas concentrating in a cascade with recycling of the retentate.