the aim of this study was to determine the monthly dtr mass load of amphetamine-type compounds in poland as well as an investigation of cyclical behaviour by using time series analysis and especially trends analysis.amphetamine, methamphetamine and mdma (ecstasy) were detected in wastewater samples collected from the main wastewater treatment plant in the city of poznan using liquid chromatogra...

The representation of data, whether geophysical observations, numerical model output or laboratory results, by a best fit straight line is a routine practice in the geosciences and other fields. While the literature is full of detailed analyses of procedures for fitting straight lines to values with uncertainties, a surprising number of scientists blindly use the standard least-squares method, ...

During the fitting of a multi-exponential model to experimental visco-elastic stressdecrease curves determined after stepwise straining of urinary bladder-wall tissue, Coolsaet et al. [l] noted a discrepancy between the results obtained with the two computer programs used to estimate the parameters of the multi-exponential model (i.e. the coefficients and exponents of the various exponential te...

Imputation of missing data is of interest in many areas such as survey data editing, medical documentation maintaining and DNA microarray data analysis. This paper is devoted to experimental analysis of a set of imputation methods developed within the so-called least-squares approximation approach, a non-parametric computationally effective multidimensional technique. First, we review global me...

We investigate how a straight skeleton can be used to approximate a motorcycle graph. We explain how to construct a planar straight-line graph G such that the straight skeleton of G reveals the motorcycle graph of M , for every given finite set M of motorcycles. An application of our construction is a proof of the Pcompleteness of the construction problem of straight skeletons of planar straigh...

A functional relationship between two variables, applied mass to a weighing platform and estimated mass using Multi-Layer Perceptron Artificial Neural Networks is approximated by a linear function. Linear relationships and correlation rates are obtained which quantitatively verify that the Artificial Neural Network model is functioning satisfactorily. Estimated mass is achieved through recallin...

The rapid extraction of farmland boundaries is key to implementing autonomous operation agricultural machinery. This study addresses the issue incomplete boundary segmentation in existing methods, proposing a method for obtaining based on unmanned aerial vehicle (UAV) remote sensing images. divided into two steps: image acquisition and line fitting. To acquire image, an improved semantic networ...

This paper presents a methodology for missing value imputation. The methodology is based on a combination of Self-Organizing Maps (SOM), where combination is achieved by Nonnegative Least Squares algorithm. Instead of a need for validation as when using traditional SOMs, the combination proceeds straight into final model building. Therefore, the methodology has very low computational time. The ...

We study smooth maps from an open subset of a real projective space to a sphere such that all germs of straight lines go to germs of circles (or points). We give a construction of such maps based on representations of Clifford algebras. It provides a complete purely geometric description of Clifford algebras representations in terms of circles. We also describe a connection between our problem ...