Development and Analysis of Long-Term Measurement Systems for Groundwater Level Using Electric Capacity

In soil dams and embankments made of soil, deterioration and stress release owing to internal and external influences occur, and the instability of the body increases as the shear strength decreases. In particular, understanding the location and flow of underground water is very important for securing the long-term stability of waterfront structures in contact with water. However, the physical limitations of measuring equipment cause many difficulties in understanding the existence and location of groundwater over a long period of time. In this study, measuring equipment using electric capacity was developed for the long-term measurement of groundwater, and contactless measuring sensors were manufactured to eliminate the possibility of corrosion by water. In addition, the precision of the measurement data was improved by applying waterproof and water-repellent coatings to the measurement sensor. Laboratory tests conducted using the developed equipment demonstrate the high precision of the measurement data according to the groundwater level change and enhanced durability of the sensor, which facilitate long-term measurements in the field.

Rapid Aging as a Key to Understand Deactivation of Ni/Al2O3 Catalysts Applied for the CO2 Methanation

We developed a rapid aging method for Ni/Al2O3 methanation catalysts mimicking the real aging in the actual application. The method is based on hydrothermal deactivation of the catalyst at 600 or 700 °C, which leads to a catalyst with nearly constant conversion after a much shorter time period compared to normal aging. The hydrothermally aged catalysts are characterized by N2 adsorption, X-ray powder diffraction, temperature-programmed reduction and H2 chemisorption. The catalytic performance of the aged catalysts is comparable to the one of a catalyst deactivated in a long-term measurement with up to 720 h on stream. The time needed for reaching a stable conversion can be diminished by rapid aging by a factor of 10. The investigations also showed that the long-term deactivation is caused by Ni particle sintering and that the support pores limit the Ni particle size. Graphical Abstract

Evaluating the Parameters of a Systematic Long-Term Measurement of the Concentration and Mobility of Air Ions in the Environment inside Císařská Cave

Determining the concentration and mobility of light air ions is an indispensable task to ensure the successful performance and progress of various operations within multiple fields and branches of human activity. This article discusses a novel methodology for measuring air ions in an environment with high relative humidity, such as that of a cave. Compared to common techniques, the proposed method exhibits a lower standard deviation and analyses the causes of spurious oscillations in the measured patterns obtained from FEM-based numerical simulations on the one hand and a model with concentrated parameters on the other. The designed ion meter utilises a gerdien tube to facilitate long-term measurement in cold and very humid spaces, an operation that can be very problematic if executed with other devices. Importantly, the applied procedure for calculating the mobility spectra of air ions from the acquired saturation characteristics is insensitive to fluctuations and noises in the measured patterns, and it also enables us to confirm the presence of very mobile air ions generated by fragmenting water droplets. During the sensing cycles, the concentration of light negative ions was influenced by the active gerdien tube. For the investigated cave, we had designed a measuring sequence to cover not only the time dependence of the concentration of light negative ions but also their mobility; this approach then allowed monitoring the corresponding impact of the patients’ presence in the cave, an effect neither described nor resolved thus far. Such comprehensive research, especially due to its specific character, has not been frequently conducted or widely discussed in the literature; the efforts characterised herein have therefore expanded the relevant knowledge and methodology, thus contributing towards further advancement in the field.

Monitoring Lower Back Activity in Daily Life Using Small Unintrusive Sensors and Wearable Electronics in the Context of Rheumatic and Musculoskeletal Diseases

Due to a sedentary lifestyle, the amount of people suffering from musculoskeletal back diseases has increased over the last few decades. To monitor and cure these disabilities, sensors able to monitor the patient for long-term measurement during daily life and able to provide real-time feedback are required. There are only a few wearable systems that are capable to acquire muscle activity (sEMG) and posture at the same time. Moreover, previously reported systems do not target back sensor and typically comprise bulky uncomfortable solutions. In this paper, we present a new wearable sensor network that is designed to measure muscle activity and posture specialized for back measurement. Special care was taken to propose a discrete and comfortable solution. The prototype only measures 3.1 mm in thickness on the spine, making this sensor system the thinnest and lightest one in the literature to our best knowledge. After testing, it was shown that the sensor system is able to acquire two surface electromyography signals concurrently, to gather acceleration and rotation speed from the patient’s lower back, and to transmit data to a computer or a smartphone via serial communication or Bluetooth low energy for a few hours for later processing and analysis.

Contactless Gait Assessment in Home-like Environments

Gait analysis is an important part of assessments for a variety of health conditions, specifically neurodegenerative diseases. Currently, most methods for gait assessment are based on manual scoring of certain tasks or restrictive technologies. We present an unobtrusive sensor system based on light detection and ranging sensor technology for use in home-like environments. In our evaluation, we compared six different gait parameters, based on recordings from 25 different people performing eight different walks each, resulting in 200 unique measurements. We compared the proposed sensor system against two state-of-the art technologies, a pressure mat and a set of inertial measurement unit sensors. In addition to test usability and long-term measurement, multi-hour recordings were conducted. Our evaluation showed very high correlation (r>0.95) with the gold standards across all assessed gait parameters except for cycle time (r=0.91). Similarly, the coefficient of determination was high (R2>0.9) for all gait parameters except cycle time. The highest correlation was achieved for stride length and velocity (r≥0.98,R2≥0.95). Furthermore, the multi-hour recordings did not show the systematic drift of measurements over time. Overall, the unobtrusive gait measurement system allows for contactless, highly accurate long- and short-term assessments of gait in home-like environments.

GNSS Double Differences Used as Beacon Landing System for Aircraft Instrument Approach

When using GNSS navigation for final approach guidance of aircraft to a landing site, the only systems currently available are differential GNSS with additional integrity data called augmentation systems. These work well when the landing site is fixed in space and well surveyed. In all other cases, augmentation systems are difficult to use. Here, we propose relative navigation based on GNSS double difference measurement to accomplish the same task, but also onto moving landing platforms or at unsurveyed locations. We call this the Beacon Landing System. Furthermore, we show long term measurement data confirming the sub-meter accuracy and results from flight tests. During the flight test we successfully used the relative navigation for aircraft guidance.

A Long-Term Stable Sensor Based on Fe@PCN-224 for Rapid and Quantitative Detection of H2O2 in Fishery Products

Hydrogen peroxide (H2O2) has been reported to be used for the illegal treatment of fishery products in order to obtain “fake” freshness. Residues of H2O2 in food may be of toxicology concern. In this study, a nonenzymatic sensor was developed based on Fe@PCN-224 metal–organic frameworks wrapped by Nafion to detect H2O2 concentration. The hybrid structure of Fe@PCN-224 was fabricated by incorporated free FeIII ions into the center of PCN-224, which was ultra-stable due to the strong interactions between Zr6 and the carboxyl group. Scanning electron spectroscopy images exhibited that Nafion sheets crossed together on the surface of Fe@PCN-224 nanoparticles to form a hierarchical and coherent structure for efficient electron transfer. Electrochemical investigations showed that the Fe@PCN-224/Nafion/GCE possessed good linearity from 2 to 13,000 μM (including four orders of magnitude), low detection limits (0.7 μM), high stability in continuous monitoring (current remained nearly stable over 2300 s) and in long-term measurement (current decreased 3.4% for 30 days). The prepared nanohybrid modified electrode was effectively applied to H2O2 detection in three different fishery products. The results were comparable to those measured using photometrical methods. The developed electrochemical method has a great potential in detecting the illegal management of fishery products with H2O2.