Kelvin probe force microscopy work function characterization of transition metal oxide crystals under ongoing reduction and oxidation

Controlling the work function of transition metal oxides is of key importance with regard to future energy production and storage. As the majority of applications involve the use of heterostructures, the most suitable characterization technique is Kelvin probe force microscopy (KPFM), which provides excellent energetic and lateral resolution. In this paper, we demonstrate precise characterization of the work function using the example of artificially formed crystalline titanium monoxide (TiO) nanowires on strontium titanate (SrTiO3) surfaces, providing a sharp atomic interface. The measured value of 3.31(21) eV is the first experimental work function evidence for a cubic TiO phase, where significant variations among the different crystallographic facets were also observed. Despite the remarkable height of the TiO nanowires, KPFM was implemented to achieve a high lateral resolution of 15 nm, which is close to the topographical limit. In this study, we also show the unique possibility of obtaining work function and conductivity maps on the same area by combining noncontact and contact modes of atomic force microscopy (AFM). As most of the real applications require ambient operating conditions, we have additionally checked the impact of air venting on the work function of the TiO/SrTiO3(100) heterostructure, proving that surface reoxidation occurs and results in a work function increase of 0.9 eV and 0.6 eV for SrTiO3 and TiO, respectively. Additionally, the influence of adsorbed surface species was estimated to contribute 0.4 eV and 0.2 eV to the work function of both structures. The presented method employing KPFM and local conductivity AFM for the characterization of the work function of transition metal oxides may help in understanding the impact of reduction and oxidation on electronic properties, which is of high importance in the development of effective sensing and catalytic devices

ENVIRONMENTAL AND PROCESS PARAMETERS OF METHANE FERMENTATION IN CONTINUOSLY STIRRED TANK REACTOR (CSTR)

A key indicator of methane fermentation process which influences the cost-effectiveness of the biogas plant is efficient production of methane per 1 m3 of reactor. It depends on the proper selection of environmental and process parameters. This article present collected and analyzed the effect of the most important parameters of continuous methane fermentation (CSTR), which include temperature, pH, nutrient content and the C/N ratio in the feed medium, the presence of inhibitors, and the volume load of reactor, retention time and mixing of digestion reactor. Still, the impact of many factors remain unknown, hence there is a need for more comprehensive studies

A preliminary assessment of soil sulphur contamination and vegetations the vicinity of former boreholes on the afforested post-mine site Jeziórko

The work aims to assess soil sulfur contamination degree indicating various reclamation efficiencies within microhabitats formed in the “Jeziorko” inoperative boreholes of former sulfur-mining areas which have been reclaimed to forest. Three plot categories have been initially determined in post-mining areas: category D – degraded, i.e. ineffectively reclaimed and unsuccessfully afforested plots, pine stands category (P), and birch stands (B), successfully afforestated. Afterwards, four circular plots were defined within each of the determined categories (4 replications, i.e. a total of 12 plots). For each plot, cover-abundance (according to the Braun-Blanquet scale) and dominant herbaceous vegetation species, tree species and stand density were determined. Height (Ht) and diameter at breast height (DBH) measurements were taken, and a vitality assessment was completed according to the IUFRO classification. Soil samples were collected at each plot from the plots in 5 points at two different depths (0–5 cm and 5–40 cm) and laboratory analysis were prepared. Soil  properties such as texture, pH, electrical  conductivity (EC), hydrolytic acidity (Hh), the contents of soil organic carbon SOC, total nitrogen TN, total sulfur TS, and exchangeable cations (Ca2+, Mg2+, K+, Na+) were determined. Soils from the D plot category were characterised by high sulfur contamination, excess salinity (EC), and strong acidity in top soil. These parameters indicated the completed neutralization had not been performed effectively at certain sites. Pine (P) and birch (B) stands categories showed good growth rates and soil parameters indicating the reclamation treatments  had been completed successfully.The work aims to assess the degree of soil sulphur contamination of the various abandoned reclamation efficiencies, within the microhabitats formed in the “Jeziórko” inoperative boreholes of former sulphur-mining areas. These areas have been reclaimed to the forest. Three plot categories were initially determined in the post-mining areas: category D – degraded, i.e. ineffectively reclaimed and unsuccessfully afforested plots, with low cover-abundance or complete lack of vegetation, pine stands category, category (P) - birch stands and category (B)- successfully afforested. Afterwards, four circular plots were defined within each of the determined categories (4 replications, i.e. a total of 12 plots). For each plot, cover-abundance (according to the Braun-Blanquet scale) and dominant herbaceous vegetation species, tree species and stand density were determined. Height (Ht) and diameter at breast height (DBH) measurements were taken, and a vitality assessment was completed, according to the IUFRO classification. Soil samples were collected at each plot, in 5 points, at two different depths (0–5 cm and 5–40 cm). Finally, laboratory analysis was undertaken. Soil properties such as texture, pH, electrical  conductivity (EC), hydrolytic acidity (Hh), the contents of soil organic carbon SOC, total nitrogen TN, total sulphur TS, and exchangeable cations (Ca2+, Mg2+, K+, Na+) were determined. Soils from the D plot category were characterised by high sulphur contamination, excess salinity (EC) and strong acidity in top soil. These parameters indicated that completed neutralization was not performed effectively at certain sites. Pine (P) and birch (B) stands categories showed good growth rates and soil parameters, indicating that the reclamation treatments were completed successfully

The Evaluation of the Possibilities of Using PLGA Co-Polymer and Its Composites with Carbon Fibers or Hydroxyapatite in the Bone Tissue Regeneration Process – in Vitro and in Vivo Examinations

Synthetic polymers belonging to the aliphatic polyester group have become highly promising biomaterials for reconstructive medicine. The purpose of the present work is a biological evaluation of lactide-glycolide co-polymer (PLGA) and its composites with carbon fibers (PLGA+CF) or hydroxyapatite (PLGA+HA). The cytotoxicity of the evaluated materials towards hFOB 1.19 human osteoblast-like cells was assessed. Moreover, during the one-year contact of the assessed materials with living osseous tissue, the progress of bone formation was analyzed and the accompanying process of the materials’ degradation was evaluated. The materials under evaluation proved to be biocompatible

Application of Machine Learning in Forecasting the Impact of Mining Deformation: A Case Study of Underground Copper Mines in Poland

Open access to SAR data from the Sentinel 1 missions allows analyses of long-term ground surface changes. The current data-acquisition frequency of 12 days facilitates the continuous monitoring of phenomena such as volcanic and tectonic activity or mining-related deformations. SAR data are increasingly also used as input data in forecasting phenomena on the basis of machine learning. This article presents the possibility of using selected machine learning algorithms in forecasting the influence of underground mining activity on the ground surface. The study was performed for a mining protective area with a surface of over 500 km2 and located in western Poland. The ground surface displacements were calculated for the period from November 2014 to July 2021, with the use of the Small Baseline Subset (SBAS) method. The forecasts were performed for a total of 22 identified subsidence troughs. Each of the troughs was provided with two profiles, with a total of more than 10,000 identified points. The selected algorithms served to prepare 180-day displacement forecasts. The best results (significantly better than the baseline) were obtained with the ARIMA and Holt models. Linear models also provided better results than the baseline and their performance was very good at up to 2 months forecasting. Tree-based models including their sophisticated ensemble versions: bagging (Random Forest, Extra Trees) and boosting (XGBoost, LightGBM, CatBoost, Gradient Boosting, Hist Gradient Boosting) cannot be used for this type of predictions since Decision Trees are not able to extrapolate and thus are not a valid stand-alone tool for forecasting in this type of problems. A combination of satellite remote sensing data and machine learning facilitated both the simultaneous quasi-permanent monitoring of ground surface displacements and their forecasting in a relatively long time period

Application of Machine Learning in Forecasting the Impact of Mining Deformation: A Case Study of Underground Copper Mines in Poland

Open access to SAR data from the Sentinel 1 missions allows analyses of long-term ground surface changes. The current data-acquisition frequency of 12 days facilitates the continuous monitoring of phenomena such as volcanic and tectonic activity or mining-related deformations. SAR data are increasingly also used as input data in forecasting phenomena on the basis of machine learning. This article presents the possibility of using selected machine learning algorithms in forecasting the influence of underground mining activity on the ground surface. The study was performed for a mining protective area with a surface of over 500 km2 and located in western Poland. The ground surface displacements were calculated for the period from November 2014 to July 2021, with the use of the Small Baseline Subset (SBAS) method. The forecasts were performed for a total of 22 identified subsidence troughs. Each of the troughs was provided with two profiles, with a total of more than 10,000 identified points. The selected algorithms served to prepare 180-day displacement forecasts. The best results (significantly better than the baseline) were obtained with the ARIMA and Holt models. Linear models also provided better results than the baseline and their performance was very good at up to 2 months forecasting. Tree-based models including their sophisticated ensemble versions: bagging (Random Forest, Extra Trees) and boosting (XGBoost, LightGBM, CatBoost, Gradient Boosting, Hist Gradient Boosting) cannot be used for this type of predictions since Decision Trees are not able to extrapolate and thus are not a valid stand-alone tool for forecasting in this type of problems. A combination of satellite remote sensing data and machine learning facilitated both the simultaneous quasi-permanent monitoring of ground surface displacements and their forecasting in a relatively long time period

Turbulent spark-jet ignition in SI gas fuelled engine

The article contains a thermodynamic analysis of a new combustion system that allows the combustion of stratified gas mixtures with mean air excess coefficient in the range 1.4-1.8. Spark ignition was used in the pre-chamber that has been mounted in the engine cylinder head and contained a rich mixture out of which a turbulent flow of ignited mixture is ejected. It allows spark-jet ignition and the turbulent combustion of the lean mixture in the main combustion chamber. This resulted in a two-stage combustion system for lean mixtures. The experimental study has been conducted using a single-cylinder test engine with a geometric compression ratio ε = 15.5 adapted for natural gas supply. The tests were performed at engine speed n = 2000 rpm under stationary engine load when the engine operating parameters and toxic compounds emissions have been recorded. Analysis of the results allowed to conclude that the evaluated combustion system offers large flexibility in the initiation of charge ignition through an appropriate control of the fuel quantities supplied into the pre-chamber and into the main combustion chamber. The research concluded with determining the charge ignition criterion for a suitably divided total fuel dose fed to the cylinder

Turbulent spark-jet ignition in SI gas fuelled engine

The article contains a thermodynamic analysis of a new combustion system that allows the combustion of stratified gas mixtures with mean air excess coefficient in the range 1.4-1.8. Spark ignition was used in the pre-chamber that has been mounted in the engine cylinder head and contained a rich mixture out of which a turbulent flow of ignited mixture is ejected. It allows spark-jet ignition and the turbulent combustion of the lean mixture in the main combustion chamber. This resulted in a two-stage combustion system for lean mixtures. The experimental study has been conducted using a single-cylinder test engine with a geometric compression ratio ε = 15.5 adapted for natural gas supply. The tests were performed at engine speed n = 2000 rpm under stationary engine load when the engine operating parameters and toxic compounds emissions have been recorded. Analysis of the results allowed to conclude that the evaluated combustion system offers large flexibility in the initiation of charge ignition through an appropriate control of the fuel quantities supplied into the pre-chamber and into the main combustion chamber. The research concluded with determining the charge ignition criterion for a suitably divided total fuel dose fed to the cylinder

Optical study of the use of recirculated gases for adiabatization of combustion process in the SIDI engine

Proper delivery of gaseous components of the charge into the combustion chamber enables controlling of combustion in the aspect of adiabatization of the process. The adiabatization obtained as result of surrounding of combustible mixture by recirculated exhaust gases should contribute to reducing formation of harmful components created during this process. The key issue here is the formation of radicals, which is not sufficiently recognized according fuels surrounded by non-combustible gases. The innovative nature of this work ensues from the experimental confirmation of so defined organizing of combustion process. Currently there are no tests concerning attempts of gas separation in the combustion chamber of engine with external source of ignition. Such separation would contribute to the increase of the adiabatization process while at the same time the combustion rate increases and reduces the combustion duration. This paper presents the next stage of research, which were preceded by simulation and experimental investigations. In the article the results of the impact of the strategy of non-combustible gas injections on combustion ratios for cylinder head with a centrally positioned ignition point have been discussed. The analysis has been based on the photo material for the period from the start of ignition to full coverage of the cylinder by the flame. Authors performed a comparative analysis (against the recorded images) of the thermodynamic indexes of the combustion process obtained from the indicator traces