Inadequacies of traditional means of human recognition along with one’s possession of unique physiological traits have paved the way for a more reliable mechanism of authentication-biometrics. A ...myriad of solutions utilizing various biometric traits has been proposed. Notably, in recent years, finger vein recognition has attracted the attention of a wider research community. Due to veins being a part of intrinsic features, it is almost impossible to replicate them. Nonetheless, there is still an inferior portion of conducted research on the discriminative power of finger vein patterns. Hence, we aspire to contribute to this particular branch of biometrics. In this paper, we primarily focus on finger vein pattern enhancement by means of adaptive Gabor filters. First, a region of interest is extracted, followed by adaptive contrast enhancement. Secondly, an orientation map is computed and used as a vein direction estimation. Subsequently, the finger vein pattern is enhanced by a convolution with a Gabor filter that locally adapts its parameters to fit the local orientation and frequency of the underlying vein pattern. Preprocessing algorithm parameters were determined using our interactive GUI tool which allows experimenting with parameter values to see their impact. The extraction phase employs SIFT and SURF features which are passed to a matching stage where we use OpenCV library built-in functions to compute feature distances. Finally, we conclude the paper with a performance evaluation based on FAR/FRR indicators and genuine/impostor distribution graphs. The research is conducted on the SDUMLA-HMT, SCUT-FVD and Vera databases. The best accuracy score for SURF features was obtained with the combination of Gabor filters at 99.94% on the SDUMLA-HMT database. The best result in case of SIFT features with Gabor filter enabled yielded an accuracy of 98.32% on the Vera database. Additionally, the achieved results confirm that utilization of adaptive Gabor filters tends to improve the over-all recognition rate. A comparison table containing our and other finger vein recognition systems from the literature is presented. Our solution has been implemented as a C++ shared library.
Surfactant liquid-membrane type sensors are usually made of a PVC, ionophore and a plasticizer. Plasticizers soften the PVC. Due to their lipophilicity, they influence the ion exchange across the ...membrane, ionophore solubility, membrane resistance and, consequently, the analytical signal. We used the DMI-TPB as an ionophore, six different plasticizers 2-nitrophenyl-octyl-ether (P1), bis(2-ethylhexyl) phthalate (P2), bis(2-ethylhexyl) sebacate (P3), 2-nitrophenyl phenyl ether (P4), dibutyl phthalate (P5) and dibutyl sebacate (P6) and a PVC to produce ionic surfactant sensors. Sensor formulation with P1 showed the best potentiometric response to four usually used cationic surfactant, with the lowest LOD, 7 × 10−7 M; and potentiometric titration curves with well-defined and sharp inflexion points. The sensor with P6 showed the lowest analytical performances. Surfactant sensor with P1 was selected for quantification of cationic surfactant in model solutions and commercial samples of disinfectants and antiseptics. It showed high accuracy and precision in all determinations, with recovery from 98.2 to 99.6, and good agreement with the results obtained with surfactant sensor used as a referent one, and a standard two-phase titration method. RDS values were lower than 0.5% for all determinations.
Water used for water supply undergoes numerous changes that affect its composition prior to entering the water supply system (WSS). Once it enters the WSS, it is subject to numerous influences ...altering its physical and chemical composition, redox potential, and microbial quality. Observations of water quality parameters at different locations within the WSS indicate that it is justified to assume that these processes take place from the source to the end user. In this study, we used the results of routine everyday analyses (EC, T, pH, ORP, chloride, nitrate, nitrite, ammonium, and bacteria) supplemented by experimental data from a one-year sampling campaign assessing the main cations and anions and stable isotopes δ2H and δ18O. Through these data, the statistical significance of the differences between the concentrations of the basic water quality parameters among different WSS locations was determined, together with the water retention time in the system. The results indicate minor changes in water chemical composition within the observed WSS, remaining below the prescribed Maximum Contaminant Level (MCL) for human consumption. However, factors such as water retention time, CaCO3 deposition, pH fluctuations, and bacterial growth may influence its suitability, which necessitates further investigation into potential risks affecting water quality.
Nitrates are one of the most common groundwater contaminants and they come from different sources. The paper presents a study of groundwater quality at Varaždin wellfield in the north part of ...Croatia. The nitrate concentration at this location has been above the maximum allowed concentration for several decades, which has made the opening of new wellfields costly. Based on the previously developed groundwater flow model, a model that covers the narrow area of the wellfield is developed. The influential zone of the observed wellfield in working conditions is determined. Based on the developed model, the sources of nitrate pollution are located, which can be generally divided into non-point and point sources. Considering the time of groundwater retention in the horizontal flow, it is concluded that the water protection zones are marked following the applicable ordinance. Based on the developed groundwater flow model at the observed wellfield, a simulation of nitrate pollution propagation by advection and dispersion processes is performed. The simulation results point out the location of the poultry landfill as the largest source of nitrate pollution. However, poultry farms, which are located in the influence area of the wellfield, also contribute significantly to the nitrate concentration at the wellfield.
Inorganic perovskite CaMnO
3
${{}_{3}}$
was proposed as a substitution for the TiO
2
${{}_{2}}$
anatase in electron transport layers of solar cells containing the hybrid perovskite CH
3
${{}_{3}}$
NH
...3
${{}_{3}}$
PbI
3
${{}_{3}}$
based on increased mobility of electrons and better optical matching. Due to a suitable band gap concerning the absorption of sunlight, we investigate the potential of CaMnO
3
${{}_{3}}$
and similar manganite perovskites, where Ca is replaced by either Sr, Ba or La, as an absorber layer in inorganic perovskite solar cells. In this study, we have used optical measurements on the synthesized AMnO
3
${{}_{3}}$
(A=Ca, Sr, Ba, La) samples to aid density functional theory calculations (DFT) in order to accurately simulate the electronic and optical properties of AMnO
3
${{}_{3}}$
compounds and gauge their potential for the role of absorber layer. Both experimental measurements and theoretical calculations show suitable band gap of 1.1‐1.5 eV, depending on the compound, and absorption coefficients of the order of
105
${{10}^{5}}$
cm
-1
${{}^{-1}}$
in the visible part of the spectrum.
Potential of AMnO3 perovskites is explored and analysed using density functional theory calculations and supported by experimental measurements. They show absorption coefficients of the order 105 cm−1, which could potentially be used as a stable inorganic perovskite solar cell.
The aim of this paper is to analyse the influence of a groundwater pumping rate on nitrate concentrations at the Bartolovec wellfield, which is part of a water supply system of the town of Varaždin, ...Croatia. Over the past 16 years both the pumping rate and nitrate concentrations have increased at the wellfield. The nonlinear models that describe the pumping rate to nitrate concentration levels were developed on the basis of Logistic, Gompertz, and Richards growth functions. For each function, three different types were established regarding the initial lower contamination limit parameter. The conditions that models have to meet were defined and their reliability was established. The models were implemented on the experimental data collected during the period under consideration. The models were validated and mutually compared using Akaike’s Information Criteria (
AIC
c
), while the data fitting was estimated by using a coefficient of determination. After the results were obtained by using different models, they were compared to the maximum allowable nitrate concentrations (
MAC
) in water for human consumption. The dependence of nitrate concentrations on a pumping rate was confirmed and the reliable model for nitrate concentration on pumping rate was created. The model was calibrated and tested on the experimental data. The model exhibits asymptotic behavior and result shows that with the further increase in the pumping rate of groundwater drainage at the Bartolovec wellfield, nitrate concentrations will not exceed the MAC value providing there are no new sources of contamination in the zone of a pollutant influence.
The localization of pollution sources is one of the main tasks in environmental engineering. For this paper, models of spatial distribution of nitrate concentration in groundwater were created, and ...the point of highest concentration was determined. This point represents the assumed location of the pollution source and differs from the actual location, so there is a certain distance between the measured and assumed location. This paper puts forward a new hypothesis that the distance between the measured and the assumed location is a function of the variance of the estimation error. The scientific contribution of this paper is based on the fact that the interaction of statistical and geostatistical methods can locate the dominant point source of pollution or narrow down the search area. The above hypothesis is confirmed by the example of the Varaždin wellfield, which was closed due to an excessively high groundwater nitrate concentration. Seven different interpolation methods were used to create spatial distribution models. Each method provides a different model, a different variance of the estimation error, and estimates of the location of the pollution source. The smallest value of variance of the estimation error of 1.65 was obtained for the minimum curvature interpolation method and the largest value of variance (24.49) was obtained for the kriging with logarithmic variogram. Our results show a nonlinear and monotonic relationship between the distance and the variance of the estimation error, so logarithmic and rational quadratic models were fitted to the scatter point data. The models were linearized, a t-test was performed, and the results show that the models can be considered reliable, which is confirmed by the values of the coefficients of determination of the linearized models, which are around 0.50. The obtained results can be used in planning additional research work to determine the measured location of the pollution source. The research methodology we used is universal and can be applied to other locations where high concentrations of certain contaminants have been detected in groundwater in alluvial aquifers.
In geotechnical practice, it is often necessary to improve the properties of soil and rock in which different structures are built. For this purpose, spherical cavity blasting can be applied to ...expand the borehole. Such expansion may incorporate various constructive elements such as anchors and thus stabilize the slope. The paper presents the method for determining the increased volume, expansion, and deepening of the borehole as a result of spherical cavity blasting. In addition, mathematical models describing the dependency of the borehole expansion on the amount of explosive charge are presented. The models are mutually compared with the Akaike information criterion.
Transport layers in perovskite solar cells are the crucial parts in charge carrier extraction and transfer in the solar cell circuit. The physical and chemical properties of their interfaces with ...neighbouring layers, such as buffer layers, govern the dynamics of electrons across the interface boundaries. Using ab initio calculations, we study in detail the interface properties of metal oxide/BaTiO3 heterostructures. The structural changes near the metal oxide/BaTiO3 interfaces are detailed for the first time. The electronic properties are used to assess the quantities of interest for use in perovskite solar cells (band gap, effective mass, carrier mobility, plane averaged electrostatic potential, band offsets). The analysed results introduce several competing quantities which influence the charge dynamics: the band gap character versus the charge carrier effective mass and the averaged electrostatic potential difference versus the unfavourable conduction band offset. While experimental studies are unable to distinguish the relevance of the competing factors, our results point to the fact that BaTiO3 interlayer morphology plays a more important factor in the cell's performance than its intrinsic properties. Based on the results, general insights are given on the structural requirements for improved buffer layer materials in combinations with metal oxide transport layer used as substrates in the solar cell architecture.
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In this paper, a novel approach of modelling time series of nitrate concentrations in drinking water by nonlinear growth functions is proposed. An almost constant increase in the average values of ...nitrate concentrations occurred at the Vinokovščak wellfield in the county of Varaždin, Croatia, in the period between 1998 and 2013. Our hypothesis was that the time series would be well adjusted to the nonlinear growth function with asymptotic properties after smoothing performed by the moving average method. We used a general growth model which does not have asymptotic properties and the logistic, Gompertz and Richards functions which do have asymptotic properties. Last three growth functions were modified based on the knowledge of a constant presence of basic nitrate concentrations in the drinking water before growth. The fit of growth curves to experimental data was assessed using
R
2
and Aikake’s information criterion. The modified growth functions gave the best fit to the smoothed time series of nitrate concentrations with
R
2
ranging from 0.9960 to 0.9986.
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