Papers by Keyword: Temperature

Abstract: Lithium-ion batteries are the preferred choice for electric vehicles (EVs) due to their high energy density, low self-discharge, thermal stability, and long cycle life. Morphology of materials is essential in assessing the effectiveness of lithium-ion battery cathodes. One effective way to evaluate cathode quality is by examining its precursor (NMC-811) morphology using SEM. Samples were taken every 20 minutes over 2 hours, revealing that longer reaction times improve the homogeneity and semi-spherical shape of the NMC-811 precursor, with increased particle density and a reduced average diameter. NMC-811 was synthesized by a calcination process at temperatures of 450°C, 600°C, and 700°C, and sintering temperatures of 800°C and 900°C. SEM analysis revealed that higher calcination temperatures resulted in a more homogeneous particle structure, with variations in holding time having minimal impact on particle shape.

Abstract: Microbially induced calcite precipitation (MICP) is a promising alternative method for improving the geotechnical properties of granular soils. The effectiveness of the MICP technique depends on several variables, including relative density and temperature. The objective of this study was to determine the effect of different initial relative densities and ambient temperature ranges on the effectiveness of MICP. After 300 and 600 hours of MICP treatment, with injection cycles occurring every 12 hours, the specimens with a relative density of 34.5% were found to be effectively cemented. In contrast, specimens with a relative density of 59.8% were found to be less cemented. A greater percentage of specimens (52.4%) were cemented at warmer ambient temperatures (20-28°C), compared to only 15.7% at cooler temperatures (16-24°C). These results suggest that the looser soil matrix and warmer temperatures facilitated CaCO₃ precipitation and resulted in greater cementation.

Abstract: Mycelium-based composite (MBC), as a new engineering biocomposite, is receiving numerous interests due to its environmental sustainability. The study aimed to address the challenge of optimizing the physical properties of MBC for a more efficient production process. The study investigated the impact of hot or cold pressing, different pressing temperatures (120 °C, 160 °C, and 200 °C), pressing pressures (low, medium and high) and sequences (before and after drying process) on the physical properties of MBC such as density, shrinkage, moisture content and hardness. Mycelium millets were mixed with kenaf, carbon carbonate, wheat bran and wheat flour. The pressing methods and sequences significantly affected the properties of the MBC. Cold pressing had no effect on reducing shrinkage and moisture content of MBC but improved density. Hot pressing increased hardness at higher temperature and pressure, with strong mycelium-substrate bonding and less porosity observed in SEM image. The post processing sequence involving drying followed by hot pressing at 200°C exhibited higher density, hardness, less shrinkage and controllable moisture content of MBC for better dimensional stability and quality control purpose. It was crucial to optimize MBC pressing techniques for specific applications and ensure that it satisfied the demanding standards of companies looking for sustainable alternatives and cost-effective production.

Abstract: Fossil fuels continue to dominate energy use, despite growing environmental concerns, underscoring the need for renewable energy solutions. Photovoltaic cells convert sunlight but lose efficiency from heat, requiring cooling methods such as photovoltaic thermal systems. Tthis study evaluated a PVT system with three serpentine tubes under varied conditions using computational fluid dynamics simulations. Testing involved water coolant flow rates of 0.001, 0.005, and 0.009 kg/s, radiation intensities of 200, 400, and 600 W/m², and tube diameters of 15 mm and 17 mm. Increasing the mass flow rate significantly reduced temperature and improved thermal efficiency, while electrical efficiency remained stable as the PV panel temperature mainly influenced it. The optimal cooling performance was achieved with a 0.009 kg/s mass flow rate and a 15 mm tube diameter at 600 W/m² radiation intensity. These findings suggest water-based cooling may increase PV system performance and reliability, especially in high solar locations.

Abstract: The main objective of this study is to optimize the reverse osmosis process in order to ensure the potabilization of water from the Oued Oum Er-Rbia, by determining the most influential parameters. To the best of our knowledge, this is the first study to apply daily PCA-based monitoring on Oued Oum Er-Rbia’s raw water to optimize membrane operation under Moroccan field conditions.To better understand the interactions between quality and hydraulic parameters influencing membrane performance, data were collected from Oued Oum Er-Rbia over multiple seasons. The parameters monitored included turbidity, salinity, temperature, and Silt Density Index (SDI), all known to affect fouling and pretreatment requirements.

Abstract: This study investigates the chemical characteristics of Eco Processed Pozzolan (ePP) and its surface modification with N, N-dimethyl dodecyl amine (oePP) at varying temperatures of 30°C, 40°C, and 50°C. Comprehensive analysis, including Fourier-transform infrared (FTIR), Field Emission Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) were employed to examine the structural, compositional, and morphological changes in ePP and oePP samples. The FTIR results revealed significant alterations in the functional groups of the modified samples, particularly in regions corresponding to alkyl and silanol groups after surface modification of ePP. XRD patterns demonstrated variations in crystallinity index, with values of 14.89%, 28.23%, 11.75%, and 15.89% for oePP at 50°C, 40°C, 30°C, and ePP, respectively. Peak analysis showed distinct differences in the crystalline phases present in each sample. FESEM images revealed enhanced surface morphology and increased particle agglomeration in the modified samples, especially at 40°C. The findings demonstrate that oePP exhibits significant potential for various applications owing to its enhanced adsorption properties, surface morphology, and structural stability.

Abstract: The results study of the accuracy of the temperature fire measurement by the sensors of the fire alarms in dynamic conditions with random temperature fluctuations, are presented. The statistical study of the accuracy measurement is based on the method of transformation of the random processes by the linear systems. The constructive approaches to optimizing and the accuracy improvement of the thermal sensors with the thermo-resistant sensitive element and the bridge measuring circuit in the dynamic conditions under random temperature fluctuations based on the choice of corresponding values of the characteristic parameter of the sensor and the constant time of its sensitive element have been proposed. Scientific novelty of the results is in the development model and in the method of analysis of the dynamic model of the thermal sensors with the thermo-resistant sensitive element in the form of a thin plate. It has been proved that the invariance of the accuracy of the ambient temperature measurement over time is possible. The obtained results allow solving the practical tasks determining the optimal parameters of the sensors under the conditions of fire temperature dynamics, taking into account the background random temperature fluctuations.

Abstract: The need to study the fire hazard of typical premises of a mobile communications base station was substantiated, in particular, regarding the feasibility of equipping it with an automatic (self-contained) fire-fighting system. Criteria for assessing the fire hazard of a mobile communications base station were developed. It was experimentally established that the greatest fire hazard in the premises of a mobile communications base station was related to the following devices: Alarm Box switching panel, input and distribution board, internal air conditioner unit and 12 V 100 A#2 batteries. Moreover, the latter two ones contribute to the spread of fire inside the premises. During the ignition of the 12 V 100 A#2 batteries, it was established that the surface of the outer wall further heated to a temperature of 80 °C, which did not exceed the critical one. Thus, the fire did not spread beyond the premises. It was established that equipping the premises of a mobile communications base station with a fire-fighting system in order to prevent the fire spreading beyond its boundaries was unreasonable.

Abstract: This scientific study presents experimental results of particle agglomeration and dispersing processes under various physicochemical conditions, focusing on the effects of temperature, particle concentration, and medium viscosity. Using numerical approaches and experimental data, patterns describing the changes in agglomeration rate and the features of dispersing system stability were identified. The key findings of the research include: the influence of temperature on agglomeration, high particle concentration, medium viscosity, dispersion under low particle concentration conditions. It is noteworthy that the results also confirm an exponential dependence of the agglomeration rate on temperature. However, at high particle concentrations, this effect is mitigated by the dominance of interparticle interactions, such as Van der Waals forces and electrostatic effects. Furthermore, in systems with low particle concentration and elevated temperature, agglomeration processes significantly slow down, indicating improved dispersing stability. The study opens new perspectives for controlling particle agglomeration and dispersing based on temperature, concentration, and the physical properties of the medium. The obtained data can be useful for improving existing technologies and developing new ones in areas where controlling the behavior of dispersed systems is essential.

Abstract: The construction, operating principles, and Li-ion battery thermal runaway mechanisms were analyzed. The external mechanical damage to a Li-ion battery with the uncontrolled thermal runaway development was investigated. The battery self-heating temperature regime was determined. A possible reactions set leading to intense materials self-heating and decomposition was considered. The battery self-heating stopping by immersing it in a container with a water excess relative to the stoichiometric amount for the lithium metal maximum mass that can accumulate was investigated. The change in resulting aqueous solution pH was measured, and the hydrogen release was also recorded. Reaction completion time dependences was established. The water required amount to absorb the heat that could be released during the reaction was calculated, which correlated with the experimental data. Possible measures to Li-ion batteries prevent and stop the burning were considered.