Sample Surface Research Articles

Estimation of top soil properties by Sentinel-2 imaging

ABSTRACT This study evaluated the feasibility of using free multispectral remote sensing data from Sentinel-2A satellites to predict soil properties in Northern Karnataka, India. Sentinel-2A images were downloaded for selected sites, covering Vertisol, Ultisol, and Alfisol soils. Multiple linear regression (MLR) models incorporated four Sentinel-2 bands and six spectral indices (NDVI, GNDVI, SAVI, TVI, EVI, and BI) as independent variables, with soil properties as dependent variables. Surface samples (0–15 cm depth) were collected from March to May 2022. The analysis showed significant correlations between individual bands and soil properties, with variations in Organic Carbon (OC) compared to sand, silt, clay, and pH. Sand positively correlated with all spectral indices, while silt, clay, and pH were negatively correlated. The red and Near-Infrared (NIR) bands showed a non-significant relationship with OC. No significant correlation was found between EVI and the soil properties. Strong regression coefficients were observed between Sentinel-2 predictions and laboratory measurements: sand (r² = 0.63), silt (r² = 0.73), clay (r² = 0.59), and pH (r² = 0.59). These results demonstrate the potential of Sentinel-2 data for predicting soil properties, offering a valuable tool for managing unsampled agricultural fields.

Influence of Water Vapor and Local Gas Velocity on the Oxidation Kinetics of In625 at 900 °C: Experimental Study and CFD Gas Phase Simulation

AbstractThe effect of water vapor content on the oxidation behavior of In625 at 900 °C in synthetic air was reported. The higher the water vapor content, the greater the oxidation and volatilization rates were. Increasing the water vapor content led to an increase in the proportion of spinel and rutile-type oxides in the oxide scale compared to chromia, and the proportion of Al-rich oxides within the alloy. A kp-kv mass variation model was used to quantify the experimental results, and Fluent Ansys® CFD simulations of the gas phase were used to predict volatilization rates. CFD simulations were used to calculate local gas velocity, temperature and composition along with local volatilization rates at each point on the sample surface. It was possible to explain not only the variations in volatilization between upstream and downstream samples, but also the increased volatilization at sample corners. For longer durations, it was shown experimentally that the rate of volatilization decreases. This was explained by the enrichment of the oxide scale with spinel and rutile-type oxides.

An enhancement of the yield strength and hardness in the friction stir welding of AZ31/AA3105 joint

The objective of this research is to optimize the yield strength and hardness of AZ31/AA3105 joint during the single pass friction stir welding (FSW). For this purpose, Taguchi method was used to examine the influence of FSW parameters such as rotating speed, linear speed, advancing side and shoulder diameter on the hardness and yield strength of the welding. The microstructure of the joint has also been analyzed by optical and scanning electron microscopy (SEM) to evaluate the joint quality. The results of microstructure analysis indicated that a high quality joint with thin intermetallic layers obtained at rotating speed of 1100 rpm and linear speed of 30 mm/min. The optimization results indicated that the hardness (78.06 HV) and yield strength (129.2 MPa) can be improved simultaneously with the advancing side of Mg, rotating speed of 1100 rpm, linear speed of 30 mm/min, and shoulder diameter of 15 mm. The fracture surface of samples indicated that a combination of brittle and ductile fracture was occurred at rotating speed of 1100 rpm and linear speed of 30 mm/min, which improved the ductility and toughness. It was concluded from the obtained results that a high-quality joint with improved mechanical properties can be obtained between AZ31 and AA3105 alloys in the optimal conditions of FSW parameters.

Piezo tube stacked scanning tunneling microscope for use in extreme and confined environments

Scanning Tunneling Microscopy (STM) is widely used for observing atomic structures due to its ultra-high spatial resolution. As the core units of STM, the coarse stepper motor and imaging unit, have conflicting size requirements for piezo tubes. Longer piezo tubes yield greater output force and easier movement for the motor, while shorter tubes enhance imaging precision and stability for the scanner. Traditional STMs typically employ a large piezo tube for coarse stepping and a smaller one for independent imaging to address this issue. Here, we present the new design of a piezo tube stacked STM, in which two independent piezo tubes act together during tip-sample approach process and only one shorter tube works during scanning imaging. Both tubes are fixed to the framework, ensuring high rigidity and compactness. The new design enables us to achieve both coarse stepping and imaging functions with a total length of only 25 mm for the two tubes, effectively reducing the length of whole STM, facilitating its integration into narrow low-temperature spaces for imaging applications. Using this device, we obtained high-quality atomic images of graphite sample surfaces at room temperature. Continuous scanning imaging of the same area on Au film at 300 K demonstrates the STM’s high stability in both X-Y and Z directions. Atomic images, I-V spectra, and di/dv spectra obtained at 2 K on graphite surface illustrate the excellent application potential of this device in low-temperature environments. Finally, atomic images obtained of graphite in sweeping the magnetic fields from 0 T to 11 T in a huge vibrational dry magnet prove the new STM’s excellent performance in extreme conditions.

Managing the largest school-based COVID-19 outbreak: insights and mitigation strategies

The COVID-19 pandemic, caused by SARS-CoV-2, has significantly impacted educational environments due to their role in community transmission. Early reports indicated low transmission rates in schools, but subsequent studies showed variability, including significant outbreaks like the one in Israel. This study investigates a large COVID-19 outbreak in a boarding school in Brazil, analyzing transmission dynamics and the effectiveness of control measures such as mass testing and isolation. A total of 291 individuals from the school community were tested, revealing an overall infection rate of 64.6%. Initial cases were identified through antigen testing, followed by extensive RT-qPCR testing. Mass testing and timely isolation of infected individuals significantly reduced transmission rates. Whole-genome sequencing was performed on seven positive samples, and environmental contamination was confirmed, with 11 of 35 surface samples testing positive for SARS-CoV-2. The outbreak was controlled within 30 days through rigorous testing, isolation, and environmental disinfection. The study emphasizes the importance of mass testing, including asymptomatic individuals, and highlights the role of environmental contamination in transmission. The findings contribute to understanding COVID-19 outbreaks in educational settings and provide practical insights into managing future outbreaks through comprehensive testing and control strategies. These results may guide policymakers and public health officials in improving pandemic response measures in similar environments.

Comparison of Roka Atlas® System Performance and Health Canada Reference Method for Listeria Detection from Plastic, Sealed Concrete, and Stainless Steel Surface Samples.

There is a high demand in food industry and public health for rapid automated methods capable of high volume sample processing. In an unpaired study Roka Atlas® System performance was compared with Health Canada reference method MFHPB-30 for Listeria spp. (LSP Roka assay) and Listeria monocytogenes (LmG2 Roka Assay) detection on plastic (PL), sealed concrete (SC), and stainless steel (SS) surfaces (45 samples each per candidate or reference method). Seeking shorter enrichment time for the candidate method, R2 medium pre-enrichment for 14, 16, and 24 h at 35 °C was combined with the Roka assay. Listeria welshimeri, L. innocua, and L. monocytogenes were employed to individually inoculate each of the three surfaces, with two competing microorganisms within the 10-100 fold higher concentration range. False negative, false positive, sensitivity and specificity were 0, 0, 100, and 100%, respectively, for the plastic, sealed concrete, and stainless steel surfaces, regardless of inoculation level (high, low, and uninoculated) and enrichment time. Candidate method detected 10, 7 and 9 true positives, versus 10, 6 and 10 by the reference method in individually inoculated SS, PL and SC, respectively. Probability of detection for all the three surfaces for the Roka Atlas® System was comparable to the reference method, in this unpaired study. The Roka Atlas® System detected targets after as little as 14 h enrichment.Surface type did not negatively affect assay sensitivity or specificity.The Roka Atlas® System was comparable to the reference method.

Theoretical study on the effect of temperature gradient on contact-free scanning for scanning ion conductance microscopy

Scanning ion-conductance microscopy (SICM) is a non-contact, high-resolution, and in-situ scanning probe microscope technique, it can be operated in probing the physical and chemical properties of biological samples such as living cells. Recently, using SICM to study the effects of microenvironment changes such as temperature changes on response of the biological samples has attracted significant attention. However, in this temperature gradient condition, one of the crucial but still unclear issues is the scanning feedback types and safe threshold. In this paper, a theoretical study of effect of the temperature gradient in electrolyte or sample surface on the SICM safe ion-current threshold is conducted using three-dimensional Poisson-Nernst-Planck, Navier-Stokes and energy equations. Two temperature gradient types, sample surface and two types of pipettes with different ratio of inner and outer radii are included, respectively. The results demonstrate that the local temperature of the electrolyte and then sample surface significantly affect the ion flow, shape of the approach curves and thus safe threshold in SICM pipette probe for contact-free scanning. There is a current-increased and decreased phases for approaching the surface with higher temperature and two current-decreased phases for surface with lower temperature. Based on this shape feature of approach curves, the change rate of current is analysis to illustrate the possibility for contact-free scanning of slope object. The results indicate that with the decrease of the normalized tip-surface distance, the coupling effect of large slope angle and local high temperature makes the increase in change rate of ion current not significant and then it challenging to realize contact-free scanning especially for higher surface temperature.

Thermal Stress Analysis of Compact Heat Exchanger Produced by Additive Manufacturing

Abstract Compact heat exchangers are renowned for their high heat transfer rates and efficiency, achieved by incorporating mini and micro-channels in their core design. However, operating under conditions of high-pressure fluctuations and significant temperature differences between hot and cold streams can potentially induce fatigue failure. To the best of our knowledge, this study represents the first investigation into the thermal stresses experienced by heat exchanger samples manufactured by selective laser melting technology, focusing on circular channels. Experiments were conducted using hot water in the inner channel, while the remaining channels and the sample surface were subjected to natural convection in ambient air. Strain gauges, thermocouples, and RTDs were employed to measure strain and temperature variations over time. These data were utilized as inputs for a numerical model based on finite element method. The strain measurements were compared with those obtained from the numerical model, revealing an average difference of approximately 20%. Lastly, a thermal fatigue analysis based on the maximum equivalent stresses predicted by the numerical model is presented. The evaluation considered both S-N curves: outlined in the ASME standard and the one obtained with specimens produced through selective laser melting. In the case of circular channels manufactured through additive manufacturing evaluated in this work, thermal stresses alone are insufficient to cause component failure due to fatigue. However, significant pressure cycles superimposed on the model can reverse this situation, making the combined effect of thermal and mechanical stresses influential in determining the component's fatigue behavior.

Aerobic anoxygenic phototrophic bacteria correlate with picophytoplankton across the Atlantic Ocean but show unique vertical bioenergetics

AbstractAerobic anoxygenic phototrophic (AAP) bacteria are a common part of microbial communities in the sunlit ocean. They contain bacteriochlorophyll a (BChl a)‐based photosystems that harvest solar energy for their metabolism. Across different oceanic regions, AAP bacteria seem to be more abundant in eutrophic areas, associated with high chlorophyll concentrations. While most previous studies focused on surface samplings, there is limited information regarding their vertical distribution in euphotic zones of the major ocean basins. Here, we hypothesized that AAP bacteria will follow a similar structure to the chlorophyll depth profile across areas with different degrees of stratification. To test this hypothesis, we enumerated AAP cells and determined bulk water BChl a concentrations along the photic zone of a latitudinal transect in the South and Central Atlantic Ocean. Overall, the distribution of AAP bacteria was highly correlated to that of chlorophyll a and to the abundance of picophytoplankton across both vertical and horizontal gradients. Furthermore, estimated light energy captured across the water column showed that, while AAP bacteria share a common latitudinal pattern of light absorption with picophytoplankton, they display a unique vertical arrangement with highest photoheterotrophic activity in the top 50 m of the surface ocean.

Organic compounds as temperature calibrants for fast scanning calorimetry

Organic compounds can be used as temperature calibrants in fast scanning calorimetry. Their advantages include ease of surface cleaning of the calorimetric chip and good thermal contact with the chip surface. Among several compounds tested, benzoic acid was identified as a convenient and reliable calibrant for temperatures below approximately 130 °C. However, organic calibrants often exhibit unusual heating rate dependencies of the onset temperatures of melting. This phenomenon can be semi-quantitatively explained by considering different heat flows within the sensor. Notably, the thermal resistance between the heater and thermopile, often overlooked, introduces an additional time constant that can sometimes result in a negative apparent thermal lag. In addition, the onset temperatures are influenced by factors such as sample position, thickness, surface wetting, and spreading. These factors limit the accuracy of transition temperature determinations to approximately ±1 K below 130 °C and ±5 K up to 220 °C.

CFRTP single-lap adhesive bonding and its mechanical performance enhanced by laser surface treatment: Finite element simulation and experimental validation

The outstanding mechanical properties of carbon fiber reinforced thermoplastic polymer (CFRTP) have led to its widespread application in many industrial sectors. In response to the engineering challenge of repairing large non-critical CFRTP structural components in situ, an infrared fiber laser surface cleaning technology is proposed to treat the bonding interface and enhance the tensile strength of polypropylene (PP)-based CFRTP single-lap bonded joints. Specifically, through single-factor and orthogonal experiments, the impact of different process parameters on the properties of the bonded joints was identified first. Then, online temperature monitoring was performed to elucidate the laser treatment mechanism of the CFRTP sample interface. Surface morphology of the laser-treated samples further indicates that when the temperature of the sample surface surpasses the resin decomposition temperature with extended holding time, the resin could be removed from the surface more thoroughly. Additionally, a novel three-dimensional woven finite element (FE) model, accounting for anisotropic heat transfer, was established to predict the surface temperature and cleaning quality of CFRTP. The FE model incorporates the anisotropic heat transfer characteristics of carbon fibers, thus accurately simulating the heat transfer behaviors between carbon fibers and the resin matrix. The laser ablation mechanism is elucidated by examining the surface ablation morphologies and peak surface temperatures. A comparison between experimental results and FE simulations demonstrated a notable coherence in the trend of surface morphology variations, with discrepancies in peak surface temperatures ranging from 3.29 % to 24.63 %. The experimental tests proved that the shear strength of single-lap bonded joints reaches its maximum value when the laser power is 35 W, the scanning speed is 2500 mm/s, and the number of scans is four. The enhancement of the mechanical properties of bonded joints can be attributed to the improved wettability and higher surface free energy of the laser-treated samples.

Optimization of the interfacial properties between mechanically and electrochemically treated aluminium and nano-modified coatings for printed outdoor applications

The aim of this research was to analyze the interfacial properties between the surfaces of mechanically and electrochemically treated aluminium substrates and the printed coatings modified by the addition of silicon dioxide (SiO2) and titanium dioxide (TiO2) nanoparticles. The nanoparticles were added to the printing inks in various concentrations with the scope to optimize the interface properties of the prints for outdoor applications. The surface, as well as the structural and mechanical properties of the printed coatings were evaluated. Various methods were employed to measure and analyze the surface and interfacial properties of aluminium and coatings. Surface microphotographs and the roughness of the treated aluminium substrates were examined, the surface free energy of the aluminium and the coatings as well as the adhesion properties were calculated, and the thickness and optical density of the coatings were measured. Considering that the treated aluminium samples prepared for this research had quite textured and different surfaces, the contact angles used for the calculation of surface free energy were calculated with and without Wenzel model to obtain detailed information about the interactions between the surface of aluminium samples and the printed modified coatings. The results showed that the type of treatment of aluminium substrates as well as the modification of the printing inks have a significant influence on the adhesion and surface properties of the coatings considered. Furthermore, the results demonstrated that the produced nano-modified coatings can be used as printed coatings or as customized primers for applying various types of inks and coatings.

The effect of oxidation on tribology behavior of nickel-graphite coated stainless steel SS420

The main solution to the challenge of maintaining maximum sealing in the compressor section of each gas turbine is the use of abradable coatings. These coatings have a double duty, including (a) maintaining the lagging and (b) protecting the tips of the rotor blades. Choosing the type of abradable coating primarily depends on the service temperature of the coating. Nickel-graphite (Ni-G) coating is a good choice for use up to 480 °C and, or steel/sub-alloy rotor blades. In this research, the Ni-G coating was applied by the flame spraying method of Ni-G powder with a thickness of about 250 μm on an SS420 stainless steel substrate. The effect of the composition of the bonding layer was also investigated using two compositions, Ni-5Al and NiCrAlY. Obtaining the knowledge of applying Ni-G coating by flame spraying, identifying the structural and compositional characteristics of the coating (through optical and electron metallography), and the effect that oxidation can have on the tribological behavior of the coating were among the goals of this project. The best conditions for spraying the Ni-G coating were achieved an oxygen gas pressure of 6 bar, oxygen flow rate of 18 L min−1, acetylene pressure of 1.5 bar, acetylene flow rate of 24 L min−1, and the distance between the gun head and the sample surface was 22 cm. The results showed that placing the coating in oxidizing conditions increases its coefficient of friction. The increase in the coefficient of friction was attributed to the formation of oxide shells on the surface of the coating after 500 h of exposure to oxidation conditions. Corresponding to the higher coefficient of friction, the oxidized coating showed a decrease in wear resistance as a result of oxidation. This result can show the decrease in abradable of this coating with increasing service time.

Laser scanning patterns induced surface properties variations of Ti-V-Hf-Zr non-evaporable getter film with 316L stainless steel substrates

The effects of laser treatment scanning patterns on the properties of Ti-V-Hf-Zr non-evaporable getter (NEG) film on 316L stainless steel (316L SS) substrates were analyzed. 316L SS substrates were laser-treated with different patterns, which resulted in spherical structure and protrusions on the surface of the substrates. Subsequently, Ti-V-Hf-Zr NEG films were deposited on ultrasonically cleaned laser-treated 316L SS by a direct current (DC) magnetron sputtering machine. Based on the XPS results of Ti-V-Hf-Zr, it has been revealed that the atomic proportions of film elements on the surface of samples #1-1∼#3–1 were about 2.2 (Ti):1.7 (Zr):0.9 (V):1.0 (Hf). In this paper, the Ar+-induced secondary electron yield (SEY) and surface resistivity of Ti-V-Hf-Zr NEG are discussed for the first time, and it has been observed that the laser treatment leads to an increase of the substrate surface roughness, which decreases the SEY and increases the surface resistivity.

A self-adaption robust superhydrophobic cement mortar for resistance of cold environment

Superhydrophobic coatings have wide range of engineering applications due to its excellent wettability. However, the durability of superhydrophobic coatings is still challenging under complex environments, especially in cold regions. In this study, we prepared a new self-adaption superhydrophobic cement mortar (SSCM) by wettability modified aggregates with polydimethylsiloxane adhesive and silica nanoparticles decorated by 1H,1H,2H,2H-perfluorodecyltriethoxysilane. Subsequently, a series of multi-scale characteristics of the SSCM sample were systematically investigated, including the micro morphology, the chemical compositions, the self-adaption robustness, the anti−/de-icing properties, and the freeze-thaw (F-T) resistance. The results indicate that surface and inside of the SSCM samples exhibit a self-adaption superhydrophobicity with the 150.0° contact angle due to the low surface energy micro/nano structure of wettability modified aggregates. Meanwhile, the SSCM sample shows excellent anti−/de-icing abilities due to the stable rough micro/nano structure under negative-temperature ambient, which can delay the droplet freezing time by 4.3 times than that of the contrast sample. Additionally, the newly exposed section of SSCM sample can still have the self-adaption superhydrophobicity and endow significant F-T resistance even if the surface of SSCM was damaged. Meanwhile, the SSCM sample can improve the F-T resistance by 45 % compared to the contrast sample. This work provides a new strategy to solve the durability limitation of superhydrophobic coating in engineering practice.

Angle-dependent ion-beam etching of RuAl thin films for structuring GHz-frequency electronics

Abstract The ruthenium aluminide (RuAl) alloy is a promising electrode material for wireless surface acoustic wave sensors working under harsh conditions at high temperatures. However, during the structuring of RuAl thin films using ion-beam etching, etched material can redeposit at the edges of the electrodes and form objects, so-called fences, on top of the structured features. These decrease the high-temperature stability and lead to an undesired alteration of the sensor performance. In this work, the angle-dependent ion-beam etching of RuAl thin-films was investigated to inhibit the formation of such fence structures. The etch rate was determined as a function of the etching angle between ion-beam and sample surface in a range between 90° and 40°.
Furthermore, finger structures with pitches below 500 nm, which are required for devices working in the intended GHz regime, were patterned to study the influence of the etching angle on the profile of the RuAl electrode fingers using transmission electron microscopy and energy-dispersive X-ray spectroscopy. The results show that an etching angle of 50° results in the highest etch rate. For etching angles of 50° and below, the width of the fences is reduced below 10 nm, so they break off during standard resist removal procedures. Such low etching angles lead to shadowed areas on the side of structured features, in which unetched material remains. However, this material can be removed by using a two-step etching process combining a 50° step with a 90° step. This process is capable of structuring fence-free trapezoidal-shaped electrode finger profiles. Therefore, the developed process is well suited for the fabrication of high-temperature GHz-frequency RuAl electrodes.

Detection of SARS-CoV-2 on the environmental surfaces and its implications for pandemic preparedness

Even though death due to COVID-19 is no longer a public health emergency, less virulent but highly transmissible forms of SARS-CoV-2 continue to spread in many countries leading to outbreaks and rise in hospitalizations in the affected regions. Lessons learned during the pandemic must be put into action to protect the world's population from another catastrophe like COVID-19. Novel approaches that were developed for tracking the spread of SARS-CoV-2 included analysis of wastewater, air samples, and various environmental surfaces. We conducted a study in Kuwait during the peak of COVID-19 pandemic to examine if SARS-CoV-2 could be detected in swabs taken from frequently touched environmental surfaces. We selected 12 Cooperative Society Stores—two from each governorate of Kuwait—for collection of surface samples. The Cooperative Society Stores are widely distributed across the whole country and cater to daily household needs including groceries and other essential items. These stores operated even during the “lockdown” imposed at the height of the pandemic. We collected swabs from high-touch surfaces including the handles of the shopping carts and freezers, the elevators, the keypads of the point-of-service terminals of cash counters, and the automated teller machines. All the surfaces tested showed a variable presence of SARS-CoV-2 by reverse transcriptase quantitative PCR, showing the validity of the proof-of-concept study. Monitoring of the presence of SARS-CoV-2 by surface sampling thus offers a cheap but effective means of environmental surveillance for coronaviruses. We therefore strongly recommend the addition of surface environmental sampling as a strategy for pandemic preparedness everywhere.

Mechanical and Microstructural Characterization of AISI 316L Stainless Steel Superficially Modified by Solid Nitriding Technique

AISI 316L austenitic stainless steel superficially modified by the solid nitriding technique was investigated at different nitriding times (2, 4, 6, 8, 12 and 24 h) and at 450 °C. The microstructural characterization was conducted using scanning electron microscopy (SEM) analysis and X-ray diffraction analyses, finding the presence of Fe2–3N, Fe4N and Cr2N, among others. The mechanical behavior of the modified surfaces was carried out by developing hardness profiles and relating it with the nitride layer thickness evaluated using scanning electron microscopy (SEM), obtaining layers up to 70 µm wide. The nitrogen diffusion produced species above and below the surface sample with a transformation from the austenitic phase to an expanded austenite (γN) phase, which is responsible for producing an increase in hardness of up to 1200 HV in the samples treated at 24 h, which is four times higher than the untreated steels. Wear evaluations of the obtained layers were performed using a pin-on-disk system under zero lubrication, indicating that the samples with 12 and 24 h of treatment present the best wear resistance promoted by an oxidative–adhesive mechanism. The obtained results are positively comparable with those of the ion nitriding technique but with a lower implementation cost.

Assessment of Soil Physico-chemical Properties in Sugarcane Cultivation Areas of Navsari District, Gujarat, India

Sentinel 2 satellite data from the year 2021 were acquired from the Copernicus site to identify the sugarcane producing area in the Navsari district. Hybrid classification approach i.e., supervised and unsupervised with ground truth data were applied using ERDAS IMAGINE software. After image classification, 2.5 km x 2.5 km grid was prepared in Q-GIS software which along with classified sugarcane area were overlapped for site identification. Then, random soil surface and sub-surface samples were collected with reference from grid of intensive sugarcane growing area. The particle density (2.10 to 2.76 g cm-3 with the mean value of 2.58 g cm-3) and bulk density (1.10 to 1.68 g cm-3 with the mean value of 1.33 g cm-3) of surface soil were found to be lower than sub-surface soil (2.18 to 2.79 g cm-3 and 1.15 to 1.68 g cm-3 with the mean value of 2.62 g cm-3 and 1.42 g cm-3 respectively) while porosity (31.60 to 59.26% with the mean value of 48.39%) and maximum water holding capacity (22.77 to 51.92% with the mean value of 39.60%) of surface soil were found to be higher than sub-surface soil (29.54 to 57.71% and 20.98 to 48.91% with the mean value of 45.60% and 36.81% respectively). The pH of soil surface showed range from 6.08 to 8.37 while pH of soil sub-surface noted range of 6.00 to 8.50. The electrical conductivity of surface and sub-surface soil showed the range of 0.011 to 1.580 dS m-1 and 0.010 to 1.586 dS m-1. The soil organic carbon of surface soil ranged from 0.06 to 0.89% while that of sub-surface soil varied from 0.02 to 0.85%.

Small scale pool fires: The case of toluene

Industrial applications adopting toluene as a solvent have been largely extended in recent years, including solutions within the framework of the energy transition and energy storage technologies. The potential use of this flammable compound in a different set of operative conditions and compositions requires a comprehensive and complete knowledge of its fire behaviour and combustion kinetic. To this scope, an innovative experimental procedure applicable to liquid reactive systems was developed for this scope and implemented at different boundary conditions. More specifically, the specimen was exposed to air and heat fluxes between 7 and 50 kW/m2, at a constant sample surface of 0.01 m2, an initial sample thickness of 0.01 m, and a distance between the sample and the horizontally oriented conical-shaped heater of 0.025 m. Measurements were compared with data from the current literature, when available, demonstrating the robustness and validity of the adopted procedure. Although an increase in the external flux leads to growing mass burning rates (i.e., from 0.47 g/s to 0.85 g/s), negligible effects on the ignitability were observed. Conversely, a peak in the heat release rate at 35 kW/m2 was measured. The observed reduction at higher external heat fluxes was attributed to less effective combustion, demonstrating that the maximum expected heat flux cannot be considered as an aprioristic worst-case scenario for the evaluation of pool fires. The collected data were, then, further utilized to obtain insights on the formation of the main products, including soot tendency. Based on the collected data a simplified kinetic model suitable for the computational fluid dynamics was proposed to reproduce the chemistry of the system.