Resonant States and Classical Damping

Using Koopman's approach to classical dynamical systems we show that classical damping may be interpreted as the appearance of resonant states of the corresponding Koopman's operator. It turns out that simple classical damped systems give rise to discrete complex spectra. Therefore, the corresponding generalized eigenvectors may be interpreted as classical resonant states.     

On-line coloring and cliques covering for KK s,t -free graphs

The problem of on-line coloring of an arbitrary graphs is known to be hard. Here we consider the problem of on-line coloring in the simplified situation where the input graph is KK_s,t-free. We show that the on-line coloring algorithm with the First Fit strategy of proposed by Capponi and Pilotto in [1] is the best one for KK_1,t-free graphs (t≥3). A.Capponi and C.Pilotto have shown that this algorithm achieves a competitive ratio of t−1 while we show that it is the best possible. However for the family of KK_s,t-free graphs (s≥2, t≥2) there exists no on-line coloring algorithm with a competitive function. The problem of an on-line cliques covering for these families is hard. There exists no on-line cliques covering algorithm with a competitive function for the family of KK_s,t-free graphs (s≥ 1, t≥3). The additional assumption that the input graph is given in a connected way does not help a lot and does not change our results described above.     

A heuristic approach to the reinforcement-learning control of the one-dimensional model of an HTR core

Results of calculations are presented, which are concerned with applications of the heuristic linear reinforcement systems to the control of pebble-bed HTRs with the OTTO-loading scheme. Control results of three types of systems applications are presented and discussed. The systems were found to be satisfactory for control of the complex physical plants.     

Optimisation and significance of ATP analysis for measuring active biomass in granular activated carbon filters used in water treatment

A method for determining the concentration of active microbial biomass in granular activated carbon (GAC) filters used in water treatment was developed to facilitate studies on the interactions between adsorption processes and biological activity in such filters. High-energy sonication at a power input of 40 W was applied to GAC samples for the detachment of biomass which was measured as adenosine triphosphate (ATP). Modelling of biomass removal indicated that a series of six to eight sonication treatments of 2 min each yielded more than 90% of the attached active biomass. The ATP concentrations in 30 different GAC filters at nine treatment plants in The Netherlands ranged from 25 to 5000 ng ATP cm(-3) GAC, with the highest concentrations at long filter run times and pretreatment with ozone. A similar concentration range was observed in nine rapid sand (RS) filters. ATP concentrations correlated significantly (p<0.05) with total direct bacterial cell counts in each of these filter types, but the median value of the ATP content per cell in GAC filters (2.1 x 10(-8) ng ATP/cell) was much lower than in the RS filters (3.6 x 10(-7) ng ATP/cell). Average biofilm concentrations ranging from 500 to 10(5) pg ATP cm(-2) were calculated assuming spherical shapes for the GAC particles but values were about 20 times lower when the surface of pores >1 microm diameter is included in these calculations. The quantitative biomass analysis with ATP enables direct comparisons with biofilm concentrations reported for spiral wound membranes used in water treatment, for distribution system pipes and other aquatic environments.     

Organotin compounds in the liver tissue of marine mammals from the Polish coast of the Baltic Sea

Butyltins (BTs) and phenyltins (PhTs) were determined in the livers of marine mammals found by-caught or stranded along the Polish coast of the Baltic Sea. During the investigation an original analytical method was developed. Butyltin compounds were detected in all the liver samples, whereas phenyltins were not detected in any of the samples. The total concentrations of BTs ranged from 43.9 to 7698 ng(Sn) x g(-1) dry weight. Age-related trends to accumulate BTs in immature porpoises were found. At the same time there were no male-female differences in BTs concentrations observed. No statistically significant spatial distribution differences were found between the locations corresponding to the open Baltic Sea waters and inside the Gulf of Gdańsk, which is characterized by high maritime activity. In comparison to butyltin levels in marine mammals from other geographic regions, the samples analyzed indicate a significant degree of tributyltin pollution along the Polish coast of the Baltic Sea. On the basis of a literature review, higher BT levels are usually found in waters close to highly industrialized areas, such as Japan, Hong Kong, and the United States.     

Determination of EEG activity propagation: pair-wise versus multichannel estimate

Performance of different estimators describing propagation of electroencephalogram (EEG) activity, namely: Granger causality, directed transfer function (DTF), direct DTF (dDTF), short-time DTF (SDTF), bivariate coherence, and partial directed coherence are compared by means of simulations and on the examples of experimental signals. In particular, the differences between pair-wise and multichannel estimates are studied. The results show unequivocally that in most cases, the pair-wise estimates are incorrect and a complete set of signals involved in a given process has to be used to obtain the correct pattern of EEG flows. Different performance of multivariate estimators of propagation depending on their normalization is discussed. Advantages of multivariate autoregressive model are pointed out.     

A fuzzy-logic approach to HTR nuclear power plant model control

The fuzzy-set theory is used to incorporate linguistic ‘rules of the thumb’ of a human operator in the HTR nuclear power plant controller. The results of the extensive computer simulations are encouraging and confirm the usefulness of this approach in nuclear power plant control. In the Appendix a short introduction to fuzzy logic is given.     

Optical and chemical characteristics of the atmospheric aerosol in four towns in southern Poland

The absorption coefficient a(p) [m(-1)] as well as the mass absorption coefficient sigma(p) [m(2)/g] has been estimated for PM10 and PM2.5 in four towns located in southern Poland, based on the assumption that the reflectance of aerosol-laden filters is a good proxy for the absorptivity of aerosols. The optical properties of the airborne particles were also compared with their surface composition obtained by photoelectron spectroscopy (XPS). It was found that coarse particles, which constituted 20-30% of PM10, exhibited insignificant contribution to the absorption. The most absorptive aerosols were found in the towns located in Upper Silesia, a highly industrialized area. This reflects both the relative content of carbon in PM2.5 and the mass concentration of the fine mode. It was found that oxides and sulfates play an important role in promoting the reflectance of light from aerosols in the winter. These results support the suggestion that the revision of existing air quality standards for particulate pollution is needed.     

A versatile wavelet domain noise filtration technique for medical imaging

In this paper, we propose a robust wavelet domain method for noise filtering in medical images. The proposed method adapts itself to various types of image noise as well as to the preference of the medical expert; a single parameter can be used to balance the preservation of (expert-dependent) relevant details against the degree of noise reduction. The algorithm exploits generally valid knowledge about the correlation of significant image features across the resolution scales to perform a preliminary coefficient classification. This preliminary coefficient classification is used to empirically estimate the statistical distributions of the coefficients that represent useful image features on the one hand and mainly noise on the other. The adaptation to the spatial context in the image is achieved by using a wavelet domain indicator of the local spatial activity. The proposed method is of low complexity, both in its implementation and execution time. The results demonstrate its usefulness for noise suppression in medical ultrasound and magnetic resonance imaging. In these applications, the proposed method clearly outperforms single-resolution spatially adaptive algorithms, in terms of quantitative performance measures as well as in terms of visual quality of the images.