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Wyświetlanie 1-15 z 75
Tytuł:
Closely Intermeshing Counter-Rotating Twin Screw Extrusion of Polymers
Autorzy:
Lewandowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/115554.pdf
Data publikacji:
2011
Wydawca:
Fundacja na Rzecz Młodych Naukowców
Tematy:
Polymeric Materials
Counter-Rotating Twin Screw Extrusion
Composite Modeling
Closely Intermeshing Screw Configuration
FEM Computations
Opis:
The state-of-the-art is presented for composite modeling of counter-rotating twin screw extrusion of polymeric materials. The closely intermeshing screw configuration is considered. A new approach for composite modeling of counter-rotating twin screw extrusion is discussed. This approach is based on the three dimensional nonNewtonian FEM simulation of flow in an intermeshing modular counter-rotating twin screw extruder. Some experimental and theoretical results of the study are presented. The polymer melting behaviour and degree of filling of the screw channel during the process, as well as the pressure and temperature developments are discussed.
Źródło:
Challenges of Modern Technology; 2011, 2, 1; 36-40
2082-2863
2353-4419
Pojawia się w:
Challenges of Modern Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of errors in on-wafer measurements due to multimode propagation in CB-CPW
Autorzy:
Lewandowski, A.
Wiatr, W.
Powiązania:
https://bibliotekanauki.pl/articles/307779.pdf
Data publikacji:
2005
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
on-wafer measurements
multimode propagation
error analysis
conductor-backed coplanar waveguide (CB-CPW)
microstrip-like mode
numerical electromagnetic analysis
on-wafer probe
calibration
de-embedding
monolithic microwave integrated circuit (MMIC)
Opis:
We study for the first time errors in on-wafer scattering parameter measurements caused by the parasitic microstrip-like mode propagation in conductor-backed coplanar waveguide (CB-CPW). We determine upper bound for these errors for typical CPW devices such as a matched load, an open circuit, and a transmission line section. To this end, we develop an electromagnetic-simulations-based multimode three-port model for the transition between an air-coplanar probe and the CB-CPW. Subsequently, we apply this model to examine errors in the device S parameters de-embedded from measurements affected by the parasitic MSL mode. Our analysis demonstrates that the multimode propagation in CB-CPW may significantly deteriorate the S-parameters measured on wafer.
Źródło:
Journal of Telecommunications and Information Technology; 2005, 2; 16-22
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Multichannel Receiver of the Experimental FM Based Passive Radar Using Software Defined Radio Technology
Autorzy:
Szlachetko, B.
Lewandowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/226436.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
SDR
passive radar
GNU Radio
USRP
Opis:
In this paper we present results of research on multichannel receiver using Software Defined Radio technology. This receiver is a part of the experimental FM based passive radar being designed. The hardware platform of the receiver consists of the Universal Software Defined Radio Peripheral devices. In the paper we propose modifications of the USRP's FPGA configuration and GNU Radio code. These modifications allow for developing six/nine synchronous input channel receiver based on two/tree USRPs respectively. Issues of synchronization of separate USRP devices by assuring synchronous sampling were presented. We also propose the solution of the problem of the alignment of the data streams being sent from USRP devices via USB to the PC host.
Źródło:
International Journal of Electronics and Telecommunications; 2012, 58, 4; 301-306
2300-1933
Pojawia się w:
International Journal of Electronics and Telecommunications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Genetic structure of the old black poplar population along the bank of the Vistula River in Poland
Autorzy:
Lewandowski, A.
Litkowiec, M.
Powiązania:
https://bibliotekanauki.pl/articles/58470.pdf
Data publikacji:
2017
Wydawca:
Polskie Towarzystwo Botaniczne
Opis:
Black poplar (Populus nigra L.) is one of the main woody riparian species in Europe. Because of extensive habitat loss due to river regulations, this species is considered rare and threatened. To analyze genetic diversity and spatial genetic structure, we examined ten nuclear microsatellite loci in a population of very old P. nigra trees growing along the Vistula River in Poland. We found a high level of genetic diversity (HE = 0.792, HO = 0.731, A = 14.7) that was within the range of other natural European P. nigra populations, and our results showed that sexual propagation is the dominant way of reproduction in the studied population, leading to high clonal diversity (R = 0.91). Additionally, we did not detect a spatial genetic structure resulting in a random spatial distribution of genotypes. Individuals from such old and diverse populations have the potential to provide valuable reproductive material for both restoration programs and breeding purposes.
Źródło:
Acta Societatis Botanicorum Poloniae; 2017, 86, 1
0001-6977
2083-9480
Pojawia się w:
Acta Societatis Botanicorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Genetic status of Polish larch (Larix decidua subsp. polonica (Racib. Domin)) from Chełmowa Mountain: implications for gene conservation
Autorzy:
Litkowiec, M.
Lewandowski, A.
Burczyk, J.
Powiązania:
https://bibliotekanauki.pl/articles/2078281.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
European larch
genetic diversity
microsatellites
spatial genetic structure
Opis:
The Polish larch (Larix decidua subsp. polonica (Racib. Domin), a subspecies of European larch, is one of the most valuable forest-forming trees in Poland. It was first discovered on the Chełmowa Mountain where Natural Reserve has been established to protect this subspecies. Currently, this unique population is at risk of extinction. Nonetheless, the knowledge on the genetic diversity of this population and surround- ing larch forests is insufficient to undertake actions aimed at conservation of genetic resources. In this study, we examined the level of genetic diversity and differentiation of four subpopulations of Polish larch from Nature Reserve on the Chełmowa Mountain and surrounding areas. We used eleven nuclear microsatellite markers (SSRs) combined in two multiplex PCR reactions. In total, 344 individuals of Polish larch were genotyped and subjected to further population genetic analyses. We found the high level of genetic diversity (average: He = 0.752, Ho = 0.720) and low levels of genetic differentiation (average: Fst = 0.022). The effective population size was large and homogeneous across subpopulations (mean Ne=90.7), and we found no sign of inbreeding. The spatial genetic structure was detected in two older subpopulations but not in the younger one, suggesting its artificial origin. The old larch subpopulations were genetically homogeneous and they were related to the ancestral group of Polish lowland populations. The old larch core populations growing on Chełmowa Mountain are relatively homogeneous and they well represent the ancestral genetic group of Polish lowland larch populations. However, they still exhibit rela- tively high genetic diversity and sufficiently large effective population sizes assuring their adaptive potential for a long-term existence. Surrounding larch populations are even more genetically diverse but this might be the effect of an admixture of seed sources from various populations from a wider area of Central Europe. We recommend that specific conservation efforts should be undertaken to promote natural regeneration of the core larch populations, even supplemented by the planting of seedlings derived from the oldest larch trees. Other management actions should focus on limiting external gene flow to this unique population of Polish larch.
Źródło:
Dendrobiology; 2018, 80; 101-111
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Utility of two mitochondrial markers for identification of Picea abies refugial origin
Autorzy:
Litkowiec, M
Dering, M.
Lewandowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/41333.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
coniferous plant
tree
Norway spruce
Picea abies
mtDNA
molecular marker
mitochondrial marker
identification
polymerase chain reaction
RFLP analysis
gene pool conservation
forest ecosystem
plant population
Opis:
Picea abies (L.) Karst is one of the most important coniferous species of Europe from both ecological and economical points of view. Traditional methods for the gene pool conservation and biodiversity maintenance in forest ecosystems have been practiced in many countries. For progress in this field using highly polymorphic genetic molecular markers is needed. Our goal was to demonstrate the utility of two polymorphic mitochondrial markers mt15-D02 and nad1 b/c in identification native Norway spruce stands. This molecular markers were tested in 1401 individuals from 59 Polish Norway spruce populations. We detected three alleles, which are called1, 2 and3, for locus mt15-D02 and two alleles , which are called1 and2, for locus nad1 b/c in our material. All five variants of alleles indicate the natural origin of P. abies. Result of this study shows that molecular marker mt15-D02 is easy to use and more informative in compare to marker nad1 b/c.
Źródło:
Dendrobiology; 2009, 61; 65-71
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Trunks of multi-stem black poplars may have different genotypes – evidence from the Oder valley in Poland
Autorzy:
Zukowska, W.B.
Wojkiewicz, B.
Lewandowski, A.
Powiązania:
https://bibliotekanauki.pl/articles/2078277.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
Populus nigra
genets
ramets
conservation programs
microsatellites
Opis:
The black poplar (Populus nigra L.) is an ecologically and economically important tree species, characteristic for floodplain forests in Europe. It is now considered to be endangered in many European countries due to the loss of its natural habitat caused by the development of river engineering and intensive land use management of riverside areas. Multi-stem specimens can be found occasionally in natural black poplar populations. The percentage of such individuals is low, although in some stands it may be over a doz- en percent. The origin of multi-stem trees may be different. As a consequence, trunks being part of such a tree can have the same or different genotypes. The study aimed to find out whether all trunks of multi-stem black poplars are ramets of the same genet or if their genotypes are different, in which case they increase the gene pool of the population. We used 13 microsatellite nuclear markers to analyze the genotypes of 83 trunks belonging to 34 multi-stem black poplar trees from five natural populations from the Oder river valley in Poland. We also performed the sibship analysis of all trunks. The results showed that the trunks being part of the particular individual had distinct genotypes in five trees (14.7%). This indicates that they were formed as a result of the fusion of two genetically different individuals. The sibship analysis revealed that one multi-stem tree was represented by full-sibs. In the remaining four trees the fused trunks were not related. Nevertheless, we found three pairs of half-sibs between different trees that were distant from each other. The majority of the multi-stem trees we examined developed most probably due to the damage to the apical meristem of the main shoot of a single-stem tree. Nevertheless, some of them were indeed formed from two distinct individuals. Therefore, if a particular population consists of a small number of individuals, we recommend to study the genotypic homogeneity of each multi-stem tree.
Źródło:
Dendrobiology; 2021, 86; 1-7
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Genetic differences between two Polish populations of Pinus uliginosa, compared to P. sylvestris and P. mugo
Autorzy:
Lewandowski, A
Samocko, J.
Boratynska, K.
Boratynski, A.
Powiązania:
https://bibliotekanauki.pl/articles/41457.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
pine
genetic distance
Pinus sylvestris
Pinaceae
electrophoresis
peat bog pine
allozyme
Pinus uliginosa
Pinus mugo
genetic differentiation
Opis:
Genetic differences between two populations of P. uliginosa from Batorów and Węgliniec were assessed on the basis of 15 allozyme loci. The level of genetic differentiation between them was also compared with genetic differences among the three closely related pine taxa: P. uliginosa, P. sylvestris and P. mugo. A high level of genetic variation was found in both populations of P. uliginosa. The average (Na) and effective (Ne) numbers of alleles per locus amounted respectively to 2.47 and 1.50 in Węgliniec and to 2.67 and 1.52 in Batorów and the percentage of polymorphic loci was 80% and 87%, respectively. Close relationship between the three studied species were confirmed. The genetic differences between the two populations of P. uliginosa were substantial, as the Nei's genetic distance between the two populations (D = 0.040) was larger than between populations of P. sylvestris and between populations of P. mugo. The relatively high level of genetic differentiation between P. uliginosa populations may result from their isolation, small size and possibly different origin of these populations.
Źródło:
Dendrobiology; 2002, 48
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A 24 GHz PHEMT-based oscillator
Autorzy:
Lewandowski, A.
Kompa, G.
Mwema, W.
Wiatr, W.
Powiązania:
https://bibliotekanauki.pl/articles/309225.pdf
Data publikacji:
2003
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
generator mikrofalowy
opór ujemny
microwave oscillator
oscillator design method
negative resistance
describing function
nonlinear PHEMT model
microstrip components models
Opis:
We present a systematic nonlinear procedure for designing microwave oscillators utilising a nonlinear PHEMT model, the negative resistance approach and the describing function concept. The procedure is applied in the design of a 24 GHz oscillator, which is then realised in hybrid technology. Measurement results show - 6% shift in the frequency but an acceptable agreement in the output power. A detailed analysis shows that the frequency shift arises mainly from inadequate CAD models in the K band, for the microstrip components employed in our design.
Źródło:
Journal of Telecommunications and Information Technology; 2003, 1; 15-19
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Efficient control of coagulant dosing in wastewater treatment
Skuteczna kontrola dozowania koagulantu w oczyszczaniu ścieków
Autorzy:
Ratnaweera, H.
Smoczynski, L.
Lewandowski, A.
Bielecka, M.
Powiązania:
https://bibliotekanauki.pl/articles/807224.pdf
Data publikacji:
2005
Wydawca:
Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie
Tematy:
dosing control
coagulant
waste water treatment
drinking water treatment
Opis:
Coagulant dosing control (CDC) is necessary to ensure stable treated water quality and to reduce chemical costs both in drinking and wastewater treatment plants. The rapid development in online sensors and equipment as well as control strategies has triggered a significant development in CDC. Software sensors, streaming current detectors, charge titration units, potential dispersion analyzers etc. are now successfully used. Despite the significant advancement in the introduction and use of these novel techniques, most plants still relay on simple CDC techniques like flow proportional dosing, leaving great opportunities to reduce the coagulant costs, sludge treatment costs while achieving better treatment efficiencies overall. The paper presents a novel concept to optimize coagulant dosing control in wastewater treatment plants, and an intention to develop a widely available solution using a Polish-Norwegian Research & Development venture.
Kontrola dozowania koagulantu (KDK) jest konieczna w celu zapewnienia stabilnej jakości wody, jak i obniżenia kosztów zarówno w stacjach uzdatniania wody, jak i w oczyszczalniach ścieków. Wraz z wielkim postępem w strategii i technologii tzw. czujników „online” obserwuje się również znaczny rozwój w zakresie KDK. Zdecydowanie zwiększa się zakres czujników procesorowych, czujników w ciągłym przepływie, zestawów miareczkujących do oznaczania ładunku, analizatorów despersji itp. W przeciwieństwie do znacznego zaawansowania we wprowadzaniu i zastosowaniu tych nowatorskich technik, większość oczyszczalni ciągle opiera się na prostych systemach KDK, typu ciągłego dozowania proporcjonalnego, nie uwzględniając wielkich możliwości redukcji kosztów zużycia koagulantu i obróbki osadów, które istotnie wpływają na efektywność pracy oczyszczalni. Praca niniejsza przedstawia nowatorską koncepcję optymalizowania dawki koagulantu w oczyszczalniach ścieków oraz możliwości rozszerzenia dostępności tych rozwiązań w Polsce poprzez Polsko-Norweską Instytucję Naukowo-Rozwojową.
Źródło:
Zeszyty Problemowe Postępów Nauk Rolniczych; 2005, 505
0084-5477
Pojawia się w:
Zeszyty Problemowe Postępów Nauk Rolniczych
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Genetic evaluation of seeds of highly endangered Pinus uliginosa Neumann from Wegliniec Reserve for ex-situ conservation program
Autorzy:
Lewandowski, A
Burczyk, J.
Wachowiak, W.
Boratynski, A.
Prus-Glowacki, W.
Powiązania:
https://bibliotekanauki.pl/articles/57105.pdf
Data publikacji:
2005
Wydawca:
Polskie Towarzystwo Botaniczne
Tematy:
mating system
conservation
hybridization
Wegliniec Reserve
peat bog pine
Pinus uliginosa
conservation programme
genetic variation
Opis:
Peat-bog pine Pinus uliginosa Neumann has become extinct or rare in many parts of Europe. We have investigated the levels of genetic variation and inbreeding in seeds collected from a highly endangered reserve of this species in Poland, using allozymes as genetic markers. Generally, a high level of genetic variation was observed. The mean expected heterozygosity was 0.376, while average (Na) and effective (Ne) numbers of alleles per locus were 2.45 and 1.67, respectively. Nevertheless, we have detected relatively low levels of outcrossing, and potential biparental inbreeding. The population-wide multilocus outcrossing rate was estimated to be 0.706 (±0.091), while the minimum variance mean of single-locus estimates was distinctly lower (ts=0.611). The estimates of outcrossing calculated for individual trees ranged widely from 0.051 to 1.017, indicating the complexity of outcrossing patterns. The investigated population of P. uliginasa from Węgliniec is small and surrounded by extensive forest stands of P. sylvestris. Our three-year records of phenological observations demonstrated that flowering periods for P. uliginosa and P. sylvestris overlap, allowing for cross-pollination. The possibility of P. uliginosa pollination by P. sylvestris creates a potential danger of genetic erosion of the P. uliginosa gene pool. Nonetheless, based on a species specific cpDNA marker we have found that among 533 seedlings of P. uliginosa there were only six seedlings carrying cpDNA marker specific for P. sylvestris, indicating that such hybridization seems to be rare.
Źródło:
Acta Societatis Botanicorum Poloniae; 2005, 74, 3
0001-6977
2083-9480
Pojawia się w:
Acta Societatis Botanicorum Poloniae
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Changes in the gene pool composition of Scots pine depending on the mode of regeneration
Autorzy:
Żukowska, W.B.
Lewandowski, A.
Wójkowicz, B.
Litkowiec, M.
Rożkowski, R.
Urbaniak, L.
Kowalczyk, J.
Powiązania:
https://bibliotekanauki.pl/articles/29430785.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Źródło:
Dendrobiology; 2023, 89; 46-55
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mapping properties of a class of univalent functions with pre-assigned zero and pole
Autorzy:
Lewandowski, Z. A.
Libera, R. J.
Zlotkiewicz, E. J.
Powiązania:
https://bibliotekanauki.pl/articles/716806.pdf
Data publikacji:
1983
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Źródło:
Annales Polonici Mathematici; 1981-1983, 40, 3; 283-290
0066-2216
Pojawia się w:
Annales Polonici Mathematici
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Geographic distribution of quantitative traits variation and genetic variability in natural populations of Pinus mugo in Central Europe
Autorzy:
Boratynska, K.
Dzialuk, A.
Lewandowski, A.
Marcysiak, K.
Jasinska, A.K.
Sobierajska, K.
Tomaszewski, D.
Burczyk, J.
Boratynski, A.
Powiązania:
https://bibliotekanauki.pl/articles/41495.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Dendrologii PAN
Tematy:
geographic distribution
quantitative trait
variation
genetic variability
genetic diversity
isoenzyme
natural population
Pinus mugo
phenotypic diversity
chloroplast
microsatellite
Central Europe
Europe
Opis:
Divergence in genetic as well as phenotypic structures can be expected in species with disjunctive geographic ranges and restricted gene flow among isolated populations. Dwarf mountain pine has such a disjunctive geographic range in the mountains of Central Europe. We hypothesised that populations of Pinus mugo from the Giant Mts. differ from Alpine and Carpathian populations to a greater extent than differentiation within these regions; furthermore, these differences would be detectable at both the genetic and phenotypic levels. To verify this hypothesis, the diversity and differentiation within and among eleven populations from the Giant Mts., Carpathians and Alps were analysed using 19 isozyme isozyme loci, 17 needle and 15 cone morphological characters. Moreover, the data on 10 chloroplast microsatellites used in the previous study, were reanalysed. The differences between the three regions were greater than among populations within them. The microsatellites and isozymes clearly differentiated between regions, while in the multivariate analyses of cone and needle characters the Alpine and Carpathian populations were intermingled but distinct from those sampled in the Giant Mts. The significant genetic structuring among regions may result from an ancient fragmentation and long lasting geographic isolation between the Giant Mts., Alps and Tatras. The populations from the Giant Mts., the northernmost within the geographic range of P. mugo, presented lower level of genetic variation then those from the Alps and Carpathians. The pattern of genetic structure observed in dwarf mountain pine may be characteristic of wind-pollinated trees with a disjunctive geographic distribution
Źródło:
Dendrobiology; 2014, 72
1641-1307
Pojawia się w:
Dendrobiology
Dostawca treści:
Biblioteka Nauki
Artykuł
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