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1
Content available remote Effect of extremely severe winters on under-ice phytoplankton development in a mesotrophic lake (Eastern Poland)
Wojciechowska W., Lenard T.
Oceanological and Hydrobiological Studies
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2014
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Vol. 43, No. 2
147--153
EN
The research was carried out in a mesotrophic and dimictic lake during winters with ice cover. In the last forty years, the development of phytoplankton was analyzed in five extreme winter seasons. The studies of phytoplankton characteristics in the water column took into account values of biomass, concentration of chlorophyll-a and species composition, including dominant species. Differences in the vertical distribution of flagellate and non-flagellate species belonging to cyanobacteria and algae were analyzed in the gradient of light and thermal conditions. The phytoplankton biomass was low and vertically differentiated, with the lowest values at the deeper part of the water column. Flagellate species from the group of Cryptophyceae, Chrysophyceae and Dinophyceae were most abundant. Species biodiversity was low but every winter the dominant species represented different taxonomic groups. In some periods, larger non-motile phytoplankton species from green or blue-green algae dominated. The research proved that the development of phytoplankton under the ice cover was limited mainly by light and, to a lesser extent, by temperature.
2
Content available remote Phytoplankton diversity and biomass during winter with and without ice cover in the context of climate change
Lenard T., Wojciechowska W.
Polish Journal of Ecology
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2013
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Vol. 61, nr 4
739--748
EN
Most scenarios of the predicted climate change in Europe imply that the increasing temperature trend will be maintained in winter seasons. The presence or absence of the ice cover in winter can impact on the functioning of lake ecosystems. The research was carried out in two mesotrophic and dimictic lakes in winter with and without ice cover. The biomass and phytoplankton and its composition was analysed with reference to physical factors (PAR and temperature). The research proved that poor thermal-light conditions under the ice/snow cover favoured the development of nanoplanktonic species from the genus Cryptomonas (Cryptophyta) or Stephanodiscus (Bacillariophyceae), whereas microplanktonic species of dinoflagellates, diatoms or green algae prevailed during the ice-free winter. The highest phytoplankton biomass and species richness were recorded during ice-free winter, which affected a higher Shannon-Wiener diversity index and evenness. It has been shown that the mild winter creates good conditions for the development of phytoplankton species characteristic for the mixing periods. The lack of inverse thermal stratification during winter can lead to disturbance in the functioning of the water ecosystems throughout the year.
3
Content available remote Dystrophy or eutrophy: phytoplankton and physicochemical parameters in the functioning of humic lakes
Poniewozik M., Wojciechowska W., Solis M.
Oceanological and Hydrobiological Studies
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2011
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Vol. 40, No.2
22-29
EN
The studies were carried out in six humic lakes (Polesie Region, Eastern Poland) in order to present a role of phytoplankton in relation to physical and chemical parameters characteristic of particular processes. On the basis of physical and chemical properties of waters (SD, colour, pH, EC, Ca2+, DIC, DOC), these lakes are divided into three groups: dystrophic (Lakes Orchowe and Płotycze), humoeutrophic (Lakes Brudzieniec and Pereszpa) and mesoeutrophic (Lakes Moszne and Długie). The occurrence of dystrophication, humoeutrophication or eutrophication processes is clearly reflected in the phytoplankton composition and its abundance, as well as its biomass. In both dystrophic and humoeutrophic lakes, flagellates dominated in the phytoplankton. Among them, the invasive species Gonyostomum semen was very abundant. Mesoeutrophic lakes were characterized by other phytoplankton composition, mainly by non-flagellate species (green algae).
4
Distribution of internal heat sources in solidifying metal according to mould parameters
Szopa R., Siedlecki J., Wojciechowska W.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
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2007
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Vol. 321, z. 89
65-66
EN
The mathematical micro/macro model of pure metal solidification is considered. On the basis of direct sensitivity analysis method the mutual connections between the function controlling the course of solidification (source function) and thermophysical parameters of mould are analyzed. In the final part of paper the example of numerical computations is shown.
5
Content available remote Numerical simulation of solidification process using the Scheil model
Szopa R., Siedlecki J., Wojciechowska W.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
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2007
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Vol. 6, nr 1
253-259
EN
In the paper the macro model of volumetric solidification is discussed. The mathematical description of the process bases on a one domain approach, this means in order to take into account the evolution of latent heat, the substitute thermal capacity is introduced to the energy equation. This parameter is determined using the well known Scheil model of macrosegregation. In the first part of paper the theoretical considerations are presented, while in the second one the example of simulation are presented (solidification of Al-Si alloy is considered). The numerical algorithm bases on the finite differences method.
6
The influence of object geometry on parametric sensitivity field
Szopa R., Lara S., Wojciechowska W.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
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2006
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z. 88
257-260
7
Content available remote Second order sensitivity analysis of heat conduction problems
Szopa R., Siedlecki J., Wojciechowska W.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
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2005
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Vol. 4, nr 1
255-263
EN
In the paper the selected problems of sensitivity analysis application in the numerical modeling of heat conduction processes are discussed. The model of heat transfer bases on the Fourier equation supplemented by the geometrical, physical, boundary and initial conditions. In the first part of the paper the problems for which the second order sensitivity V (x, t) = 0, while in the next part the problems for which the second order sensitivity can be taken into account are presented, at the same time the direct approach of sensitivity analysis is used. On the stage of numerical computations the finite difference method [1] is applied.
8
Content available remote Phytoplankton of two river lakes in relation to flooding period (River Bug, Eastern Poland)
Wojciechowska W., Pasztaleniec A., Solis M., Turczyński M., Dawidek J.
Polish Journal of Ecology
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2005
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Vol. 53, nr 3
419-425
EN
Studies were carrying out in two shallow (mean depth ≈ 0.3 m) and small (area 2.7-8.2 ha) river lakes, which were flooded by water of River Bug (Eastern Poland) once a year (in spring). The species composition, biomass of phytoplankton and concentration of chlorophyll a were studied. Samples were taken in June (after flooding) and in August (after three months of isolation from river water). About 150 species of phytoplankton were determined. After the flood period phytoplankton biomass was dominated by nannoplankton belonging to Cryptophyceae and Chrysophyceae (strategy-r) and in the stabilization period by microplanktonic green and blue-green algae (strategy-K). The higher biomass and concentration of chlorophyll a values were noted in August than in June. The differentiation of phytoplankton was also stated between near-by stations in both lakes.
9
The first and second order sensitivity analysis of thermal processes with respect to cooling conditions
Szopa R., Wojciechowska W.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
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2004
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z. 78
245-248
EN
In the paper we use the sensitivity analysis methods in order to investigate the influence of external cooling conditions on the course of thermal processes proceeding in the domain considered. The model of heat transfer bases on the Fourier equation and the influence of the boundary values of heat transfer coefficient and ambient temperature on the course of cooling processes is analyzed. In order to solve a problem the direct approach of sensitivity analysis is used. On the stage of numerical computations the finite difference method is applied. In the final part of the paper the example of computations is shown.
10
Content available remote The influence of initial conditions on the course of solidification process
Szopa R., Siedlecki J., Wojciechowska W.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
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2004
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Vol. 3, nr 1
201--208
EN
The methods of sensitivity analysis are applied in order to determine the influence of pouring temperature (the initial condition) on the course of casting solidification. In the first part of the paper the macro model of the process is considered, while in the second part the micro/macro approach is taken into account. On the stage of numerical simulation the finite difference method is used. In the final part of the paper the examples of computations are shown.
11
Content available remote Sensitivity analysis of crystallization with respect internal parameters
Lupa M., Szopa R., Wojciechowska W.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
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2004
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Vol. 3, nr 1
91--98
EN
The solidification model basing on the Johnson-Mehl-Avrami-Kolmogoroff theory is discussed. Such model is called in literature 'the second generation' one. In particular the sensitivity analysis of the process with respect to the parameters appearing in the source term controlling the solidification is presented. The method allows, among other things, to analyze the influence of the 'internal' parameters on the temperature field in the system considered. On the stage of numerical computations the FDM is used. In the final part of the paper the example of computations is shown.
12
Content available remote Vertical distribution of dominant cyanobacteria species in three lakes - evidence of tolerance to different turbulence and oxygen conditions
Wojciechowska W., Poniewozik M., Pasztaleniec A.
Polish Journal of Ecology
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2004
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Vol. 52, nr 3
347-351
EN
The composition and abundance of cyanobacteria in three lakes of the Polesie Lubelskie (East Poland) were studied in summer periods. Vertical distribution of these algae was analysed in two depths - in epilimnion and deoxygenated metalimnion. Species composition and domination was similar for these two sites. It means that the species like: Limnothrix planctonica (Wołosz.) Meffert, Limnothrix redekei (Van Goor) Meffert, Planktothrixs agardhii (Gom.) Anagn. et Kom., Woronichinianaegeliana (Unger) Elenk. and Microcystis viridis (A. Braun in Rabenhorst) Lemm. are not affected by turbulence of water as well as by oxygen conditions.
13
Dehydration of exo-hydroxymethyl group in androstane derivative: optimization and scale-up
Wojciechowska W., Kutner A., Leś A., Szelejewski W.
Polish Journal of Applied Chemistry
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2004
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Vol. 48, nr 3-4
63-74
EN
Exploration of several process parameters (temperature, solvent composition, amount of concentrated HCl, scale-up factor) supported by an analysis of the reaction response surfaces fitted to the experimental data allowed to determine convenient and amenable for considerable scale-up route of dehydration of exo-hydroxymethyl group in androstane skeleton affording exemestane in high yield.
14
Content available remote Sensitivity analysis of solidification process with respect to grains geometry
Szopa R., Wojciechowska W.
Archiwum Odlewnictwa
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2003
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R. 3, nr 10
255--260
EN
In the paper the influence of the grains geometry on the course of solidification process is analyzed. In order to solve the problem the parameter sensitivity analys is has been applied. The mathematical model of thermal processes proceeding in the casting domain is constructed on the basis of the micro-macro approach. On the outer surface of the domain considered the Robin condition is assumed. On the stage of numeric al simulation the combined variant of the BEM has been used.
PL
W pracy badano wpływ geometrii ziaren na proces krzepnięcia odlewu. Rozwiązanie uzyskano wykorzystując metody analizy wrażliwości (w ujęciu bezpośrednim). Opis matematyczny procesu sformułowano w konwencji modeli mikro-makro. Na zewnętrznej powierzchni odlewu przyjęto warunek Robina. Na etapie obliczeń numerycznych wykorzystano kombinowaną metodę elementów brzegowych.
15
Sensitivity of Crystallization Process with Respect to Cooling Conditions
Szopa R., Wojciechowska W.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
|
2002
|
z. 75
159-162
EN
In the paper we use the sensitivity analysis method in order to investigate the influence of external cooling conditions on the course of casting solidification. The model of thermal processes proceeding in the domain considered corresponds to the second generation one. As an example we present the sensitivity of transient temperature field in casting volume on the changes of the mould thermal conductivity. In the final part of the paper the example of computations is shown.
16
Content available remote Second generation solidification model : sensitivity with respect to mould parameters
Lupa M., Szopa R., Wojciechowska W.
Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej
|
2002
|
Vol. 1, nr 1
97--105
EN
In the paper the solidification model basing on the Mehl-Johnson-Avrami-Kolmogorov theory is discussed. In particular the sensitivity analysis of solidification process with respect to the mould parameters is presented. The method allows, among other things, to analyze the influence of the mould parameters on the temperature field in the system considered. The casting-mould domain is treated as a 2D one. On the stage of numerical computations the boundary element method is used. In the final part of the paper the example of computations is shown.
17
Content available remote Small scale distribution and composition of phytoplankton in a shallow lake
Wojciechowska W., Solis M.
Polish Journal of Ecology
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2001
|
Vol. 49, nr 1
87-89
EN
Studies were carried out in shallow, eutrophic lake Pereszpa during vegetation season 1996. Samples were taken from the pelagic and littoral zone, where the distance between sampling sites were small (200-300 m). It was revealed in both zones quantitative and qualitative differentiation of phytoplankton during spring-summer period and homogeneity of its community in autumn.
18
Content available remote Eutrophication and winter-period structure of phytoplankton in three deep lakes in the Łęczna-Włodawa Lakeland, eastern Poland
Wojciechowska W., Pęczuła W., Zykubek A.
Polish Journal of Ecology
|
1998
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Vol. 46, no 1
89-99
EN
Studies were done in winter 1996 in three ice-covered dimictic lakes of the Łęczna-Włodawa Lakeland, eastern Poland. They involved physico-chemical conditions (temperature, oxygen concentration, pH, conductivity and Secchi-disc transparency), as well as biological ones (abundance, chlorophyll a concentration and phytoplankton structure). The oxygenation of the near-bottom layers combined with the observed structure of the winter phytoplankton confirm the rate of eutrophication of these bodies of water which had already been observed in the summer.
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