Mobility of LoRaWAN Gateways for Efficient Environmental Monitoring in Pristine Sites.

Environmental monitoring of delicate ecosystems or pristine sites is critical to their preservation. The communication infrastructure for such monitoring should have as little impact on the natural ecosystem as possible. Because of their wide range capabilities and independence from heavy infrastructure, low-power wide area network protocols have recently been used in remote monitoring. In this regard, we propose a mobile vehicle-mounted gateway architecture for IoT data collection in communication-network-free areas. The limits of reliable communication are investigated in terms of gateway speed, throughput, and energy consumption. We investigate the performance of various gateway arrival scenarios, focusing on the trade-off between freshness of data, data collection rate, and end-node power consumption. Then we validate our findings using both real-world experiments and simulations. In addition, we present a case study exploiting the proposed architecture to provide coverage for Wadi El-Gemal national park in Egypt. The results show that reliable communication is achieved over all spreading factors (SFs) for gateway speeds up to 150 km/h with negligible performance degradation at SFs=11,12 at speeds more than 100 km/h. The synchronized transmission model ensures the best performance in terms of throughput and power consumption at the expense of the freshness of data. Nonsynchronized transmission allows time-flexible data collection at the expense of increased power consumption. The same throughput as semisynchronized transmission is achieved using four gateways at only five times the energy consumption, while a single gateway requires seventeen times the amount of energy. Furthermore, increasing the number of gateways to ten increases the throughput to the level achieved by the synchronized scenario while consuming eight times the energy.

Rheological Assessment of Oil-Xanthan Emulsions in Terms of Complex, Storage, and Loss Moduli.

This experimental assessment was carried out to study the viscoelastic performance of crude oil-xanthan emulsions employing a RheoStress RS100 rheometer. Crude oil with a concentration range of 0−75% by volume was used to prepare the oil-gum emulsions. Two xanthan gums of Sigma and Kelzan were added in the emulsions with concentration ranges of 0−104 ppm. The linear viscoelastic ranges of all the tested oil-gum emulsions were found in the range of 0.1−10 Pa. Thus, the experimental tests were completed within the linear viscoelastic range of 1 Pa. The complex modulus increased gradually and steadily with frequency and gum concentration for all the examined emulsions. The addition of crude oil into the lighter xanthan concentration of <103 ppm provided almost the same behavior as the xanthan solution, whereas the presence of crude oil within the higher xanthan concentrations significantly stimulated the measured values of the complex modulus. For lower gum concentrations of up to 1000 ppm, oil concentration displayed no effect on both the storage and loss moduli, whereas for gum concentrations higher than 1000 ppm, both moduli increased gradually with crude oil concentration.

Determination of the effect of water depth on the yield of a solar still using an automatic feedwater system.

Herein, the water depth in a pyramidal solar still was kept constant using an automatic feedwater system through an auxiliary tank. Six water depths ranging from 5 to 50 mm were investigated. All variables were measured continuously but were logged automatically every hour. Increasing the water depth increased the water volume, thereby increasing the thermal capacity of the solar still. Therefore, increasing water depth increases the nocturnal yield but decreases the diurnal yield. Over the whole day, lower water depths resulted in higher accumulated yields. These accumulated yields increased by 37% by decreasing the water depth by 90% from 50 mm. The desalination system can work without human intervention, improving its sustainability. Moreover, the automatic feedwater system facilitates the end-user operation processes and succeeds in maintaining a constant optimal water depth in the solar still.

Viscoelastic Behavior of Crude Oil-Gum Emulsions in Enhanced Oil Recovery.

The experimental study of the Creep-recovery examination is necessary to understand the viscoelastic behavior of crude oil-Xanthan gum emulsions. The experimental measurements and analysis of these tests were completed using RheoStress RS100 under controlled stress CS-mode. Rheometers with CS-mode allow for a useful and direct technique for the experimental measurements of creep and recovery stages. This investigation covers a wide range of crude oil concentration of 0-75% by volume, Xanthan concentration range of 0-104 ppm, and two types of Xanthan gums are used and investigated. The creep-recovery measurements of crude oil-Xanthan gums emulsions were extensively investigated. It was important to find the linear viscoelastic range for the examined crude oil-Xanthan gum emulsions. The experimental measurements and analysis of the creep-recovery examinations showed that the linear viscoelastic range was up to 1 Pa. The experimental investigation showed that the higher the concentration of the used gum and crude oil, the lower the compliance of the emulsions. For the Xanthan concentrations of less than 103 ppm, the crude oil-gum emulsion exhibited viscous behavior. However, for the Xanthan concentration of higher than 103, the examined emulsions displayed viscoelastic behavior.

Assessment of Tree Leaves Flakes Mixed with Crude Glycerol as a Bioenergy Source.

The gasification and combustion of dry tree leaves and the cogasification of dry tree leaves soaking crude glycerol were studied experimentally. An updraft fixed bed gasification and combustion system was built. The operation was conducted at different air to fuel ratios. Results show more stable combustion and more effective heat transfer to furnace walls for the cases when tree leaves flakes are mixed with 20 percent (on mass basis) of crude glycerol, as compared with the case when only dry tree leaves are used as fuel. TGA analysis was also conducted for the two fuels used under both air and nitrogen environments. For the crude glycerol, four phases of pyrolysis and gasification were noticed under either of the two surrounding gaseous media (air or nitrogen). For the dry tree leaves, the pyrolysis under nitrogen shows only a simple smooth pyrolysis and gasification curve without showing the different distinct phases that were otherwise identified when the pyrolysis is conducted under air environment. Moreover, the air TGA results lead to more gasification due to the char oxidation at high temperatures. DTG results are also presented and discussed.