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Tytuł:
Dynamic Schemes of Hedging - Delta Hedging and Delta-Gamma Hedging on Currency Market
Dynamiczne strategie zabezpieczające - delta hedging i delta-gamma hedging na rynku walutowym
Autorzy:
Zielińska, Monika
Powiązania:
https://bibliotekanauki.pl/articles/904702.pdf
Data publikacji:
2005
Wydawca:
Uniwersytet Łódzki. Wydawnictwo Uniwersytetu Łódzkiego
Tematy:
hedging
delta hedging
delta-gamma hedging
Opis:
Dynamiczne strategie zabezpieczające przed ryzykiem walutowym to opracowane procedury czynności, które należy wykonywać na bieżąco, w sytuacjach zmian kursu waluty, w czasie ciągłego monitorowania transakcji. Jest to zatem stałe, selektywne przeciwdziałanie powstawaniu otwartych pozycji w opcjach walutowych. Preferowane są te techniki zabezpieczania, które ograniczając wysokość strat, nie wykluczają zysków kursowych. Ich stosowanie wymaga dostępu do rzetelnych prognoz przyszłych zmian cen walut, a także określonego stopnia gotowości do ponoszenia tego typu ryzyka. Artykuł prezentuje dwa rodzaje dynamicznych strategii hedgingowych: delta hedging i delta-gamma hedging wraz z przykładami dla polskiego rynku walutowego.
Dynamic schemes of hedging against currency risk are carefully structured procedures, which should be carried out immediately during continuous transaction monitoring in case of changes in currency value. Hence, it can be described as selective, continuous preventing of open positions in currency options. The hedging techniques which reduce the loss without excluding the profits from currency movements are given preference. Their application requires access to reliable forecasts of future currency movements, as well as certain readiness to bear that kind of risk. This article presents two dynamic schemes of hedging: delta hedging and delta-gamma hedging with examples from the Polish currency market.
Źródło:
Acta Universitatis Lodziensis. Folia Oeconomica; 2005, 194
0208-6018
2353-7663
Pojawia się w:
Acta Universitatis Lodziensis. Folia Oeconomica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Jezioro Aralskie - największa katastrofa ekologiczna minionego stulecia
Aral sea - the bigger ecological disaster of the century
Autorzy:
Bielecki, Rafał
Powiązania:
https://bibliotekanauki.pl/articles/471691.pdf
Data publikacji:
2010
Wydawca:
Uniwersytet Pedagogiczny im. Komisji Edukacji Narodowej w Krakowie
Tematy:
jezioro reliktowe
delta Amu-darii
delta Syr-darii
kanały nawadniające
pustynnienie
relict lake
Amu-Darya delta
Syr-Darya delta
irrigation channels
deserfitication
Opis:
One of the best examples of environmental risk arising as a result of inefficient management of environmental resources is the disappearance of the Aral Sea. Aral Sea extends into the territories of Kazakhstan and Uzbekistan. About 10 thousand years ago, this vast body of water was under the influence of water from melting mountain glaciers, flowing directly into the Aral Basin. However, the climate change which started about 3500 years ago contributed to the drying process of the tank. This process became stronger in character at the beginning of the 1960s, when due to the planned economy of the USSR, it was decided to develop large-scale cultivation of cotton in areas too dry to be suitable for such crops. Therefore, the water from the rivers Syr-Darya and Amu-Darya, flowing into the Aral Sea, was directed to irrigation, without worrying about the ecological balance. Consequently, this led to irreversible environmental changes. The Aral Sea Area decreased by 40% and its volume decreased by two-thirds. Water level dropped about 13 feet and is still falling. Historically, the reservoir was fed by more than 60 km3 of water per year; currently it is only about 5 km3. There were years when the lake received virtually no water as a result of these processes. In 1988 a division of the lake into two parts was carried out: the Big Aral Sea in the south and the Small Aral Sea in the north. The salinity of water remaining in the basin has increased roughly three fold ,which has disastrous consequences for the world’s flora and fauna. The Aral Sea region’s economy disappeared completely, e.g. the fisheries and associated processing industries, a sin water with such high salt content no organisms are able to survive. As the lake shrank and large parts of it are now dry, when strong winds blow across the land, they carry huge amounts of tiny particles of salt remaining after the water has evaporated. It has been calculated that in the year after such a dust storm around 75 million tonnes of sand mixed with salt was spread. The toxic dust destroys settlings, fields, and plants, and it is difficult to find a way to counteract this process.
Źródło:
Annales Universitatis Paedagogicae Cracoviensis Studia Geographica; 2010, 1 Dynamika zmian środowiska geograficznego pod wpływem antropopresji; 6-13
2084-5456
Pojawia się w:
Annales Universitatis Paedagogicae Cracoviensis Studia Geographica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Lacustrine deltas and subaqueous fans: almost the same, but different – a review
Autorzy:
Gruszka, Beata
Zieliński, Tomasz
Powiązania:
https://bibliotekanauki.pl/articles/1841622.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
fan delta
Gilbert-type delta
ice-contact subaqueous fan
depositional mechanisms
sedimentology
delta
mechanizmy depozycji
sedymentologia
Opis:
Although deltas and subaqueous fans are both formed in the same near-shore zones of basins, the hydraulic conditions for their formation, development and sedimentary records are different. The present review discusses the results of previously published studies of fan deltas (Gilbert-type deltas) and subaqueous fans of lacustrine and glaciolacustrine environments. The depositional mechanisms of deltas and subaqueous fans, textural and structural features of the lithofacies associations and their typical lithofacies are presented. The characteristics of subaqueous fans, which are still relatively poorly understood and are often overlooked in sedimentological interpretations of lacustrine sedimentary successions, receive particular attention. The palaeoenvironmental and lithological differences between deltas and subaqueous fans are highlighted.
Źródło:
Geologos; 2021, 27, 1; 43-55
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Adaptation of the Regularization Parameters in the Nm-Delta Networks
Autorzy:
Gołąbek, P.
Kosiński, W.
Powiązania:
https://bibliotekanauki.pl/articles/911150.pdf
Data publikacji:
2000
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
regularyzacja
Levenberg-Marquardt
NM-Delta
M-Delta
regularization
quasi-Newton
Opis:
The paper describes an application of regularization techniques to an automatic choice of parameters driving the learning process in the NM-Delta neural network architecture. The heterogeneous learning algorithm is identified as very similar to the Levenberg-Marquardt method but with a considerably smaller computational cost and different justification of parameter selection. The performance of the modified algorithm proves to be comparable with that of the Levenberg-Marquardt.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2000, 10, 4; 779-790
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Feasible star – delta and delta – star transformations for reliability networks
Autorzy:
Prasad, V. C.
Powiązania:
https://bibliotekanauki.pl/articles/262801.pdf
Data publikacji:
2017
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie
Tematy:
star–delta transformation
delta–star transformation
series parallel reliability networks
Opis:
Consider the problem of transforming a star (delta) into an equivalent delta (star) in a reliability network with imperfect undirected edges and perfect vertices. It is believed that such transformations are not possible in general if the probabilities of the elements of the given star / delta are rational numbers. Contrary to this, it is shown here that star – delta and delta – star transformations are possible under certain conditions. Further the probability of success of an element of an equivalent star (delta) is shown to be equal to the probability of failure of the corresponding element of the given delta (star).
Źródło:
Electrical Power Quality and Utilisation. Journal; 2017, 20, 1; 1-5
1896-4672
Pojawia się w:
Electrical Power Quality and Utilisation. Journal
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Establishing the Vertical Movement Map of Cuu Long Delta River by GNSS Data
Autorzy:
Nguyen, Gia Trong
Nguyen, Viet Nghia
Ly, Lam Ha
Vu, Trung Dung
Nguyen, Quoc Long
Kim, Thi Thu Huong
Pham, Ngoc Quang
Nguyen, Viet Quan
Powiązania:
https://bibliotekanauki.pl/articles/27323240.pdf
Data publikacji:
2023
Wydawca:
Polskie Towarzystwo Przeróbki Kopalin
Tematy:
land subsidence
GNSS
vertical crustal deformation
Mekong delta
deformacje
delta Mekongu
Opis:
Mekong Delta is an area with an important position in the socio-economic development of Vietnam. However, due to the impact of climate change as well as of the construction of hydroelectric dams in the upstream of the Mekong River in recent years, saline intrusion and flooding have been occurred because of high tide. According to published researches, the Mekong Delta is being experienced surface subsidence with a rate of up to centimeters per year, that exacerbates the impact of saline intrusion and flooding. Thus, studying to establish the surface subsidence map is an urgent need in this site. There are many of technologies to create the vertical movement map such as: Levelling, INSAR, GNSS, etc. Up to now, there are no scientific reports on the application of GNSS to monitor the vertical movement in this area. In this paper, the authors have calculated the largest vertical displacement velocity up to 3cm/year based on processing GNSS observations of nearly 20 GNSS monitoring station in the area using Bernese software. From these results, the research team has made the vertical movement map of Mekong, Vietnam.
Źródło:
Inżynieria Mineralna; 2023, 2; 173--177
1640-4920
Pojawia się w:
Inżynieria Mineralna
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Wyniki badań mineralogiczno-petrograficznych elementów browarów ze stanowska archeologicznego Tel el Farka, Delta Nilu, Egipt
Results of mineralogical investigation of elements of breweries, Tel el Farka archaeological site, Nile Delta, Egypt
Autorzy:
Pawlikowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/344043.pdf
Data publikacji:
2016
Wydawca:
nakł. Maciej Pawlikowski
Tematy:
Delta Nilu
mineralogia
archeologia
Tel el Farkha
Nile Delta
mineralogy
archaeology
Opis:
Wykonano badania mineralogiczno-petrograficzne i geochemiczne materiału występującego w obiektach opisywanych dotychczas jako „browary” odkrytych w stanowisku Tell el-Farkha, Kom W i kom C. Próbki pochodziły zarówno z cegieł jak i materiału znajdującego się miedzy cegłami, Badania wykazały, że temperatury wypału ceguieł i materiału znajdującego się miedzy nimi okazjonalnie w niektórych miejscach przekraczały 800o C. Ponadto małe, pojedyncze fragmenty żużelków i ziarna metalu (żelazo z tytanem) zostały odkryte w materiale znajdującym się między cegłami. Badania dowodzą, że temperatura panująca w całych obiektach była zdecydowanie zbyt wysoka do produkcji piwa.
Mineralogical, petrographical as well as geochemical investigation of so called “brewery “ discovered in Tel el Farkha archaeological site were performed. Samples of roller shape bricks as well as accompanying material for examination were collected. Examination showed temperature of firing of bricks of all discovered “brewerys” were at some places even above 800o C what is difficult obtain without additional air blowing. Observed microscopically thermal alternation of bricks of all places et examined objects was to high for production of bier. Examination confirmed at some places the presence of small fragments of Fe slag, and rare grains of metals (pure iron).
Źródło:
Auxiliary Sciences in Archaeology, Preservation of Relics and Environmental Engineering; 2016, 21; 1-13
1689-6742
Pojawia się w:
Auxiliary Sciences in Archaeology, Preservation of Relics and Environmental Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Changes in Effectiveness of Delta Hedging Using Options on the WIG20
Zmiany skuteczności hedgingu delta z zastosowaniem opcji na WIG20
Autorzy:
Węgrzyn, Ryszard
Powiązania:
https://bibliotekanauki.pl/articles/1925475.pdf
Data publikacji:
2021-01-13
Wydawca:
Uniwersytet Warszawski. Wydawnictwo Naukowe Wydziału Zarządzania
Tematy:
options
hedging delta
opcje
Opis:
Purpose: Based on the research carried out by the author in 2007 and 2015, an increase in the effectiveness of delta hedging with the use of options on the WIG20 was found. The purpose of the study is to compare the results of the 2017–2018 delta hedging effectiveness studies with the results of previous studies, as well as to assess the changes in the effectiveness with an indication of possible causes. Design/methodology/approach: To compare the effectiveness of delta hedging, the estimated Value at Risk was used for unhedged and hedged portfolios in the analyzed periods. The results obtained on the basis of data from the years 2017–2018 were compared with the results for the data from 2007 and 2015. Findings: On the basis of the conducted research, the effectiveness of delta hedging using options on the Polish market can be generally stated, but the durability of the high effectiveness of delta hedging observed in 2015 cannot be stated. In the years 2017–2018, there was a decrease in the effectiveness of delta hedging associated with a significant decrease in liquidity on the option market. The research results highlight the importance of liquidity for the proper option pricing as well as for the possibility of risk reduction. Research limitations/implications: Some difficulty and limitation of the study were quite frequent lack of data regarding the options analyzed in the period 2017–2018. Originality/value: The value of the obtained results is increased by their uniqueness, as changes in the effectiveness of delta hedging on the Polish options market are not discussed in the literature by other authors.
Cel: na podstawie przeprowadzonych przez autora badań w latach 2007 i 2015 stwierdzono wzrost skuteczności hedgingu delta z zastosowaniem opcji na WIG20. Celem pracy jest porównanie wyników badań skuteczności hedgingu delta z okresu 2017–2018 z wynikami poprzednich badań, a także ocena zmian skuteczności wraz ze wskazaniem możliwych przyczyn. Metoda: do porównania skuteczności hedgingu delta zastosowano oszacowaną wartość zagrożoną (Value at Risk) dla portfeli niezabezpieczonych i zabezpieczonych w analizowanych okresach. Wyniki uzyskane na podstawie danych z lat 2017–2018 porównano z wynikami dla danych z 2007 i 2015 roku. Wyniki: na podstawie przeprowadzonych badań można ogólnie stwierdzić skuteczność hedgingu delta z zastosowaniem opcji na polskim rynku, ale nie można stwierdzić trwałości wysokiej skuteczność hedgingu delta zaobserwowanej w 2015 roku. W latach 2017–2018 nastąpiło zmniejszenie skuteczności hedgingu delta powiązane ze znacznym spadkiem płynności na rynku opcji. Wyniki badań zwracają uwagę na znaczenie płynności dla właściwej wyceny opcji, a także możliwości ograniczania ryzyka. Ograniczenia badań: pewnym utrudnieniem i ograniczeniem badań były dość częste braki danych dotyczących analizowanych opcji w okresie 2017–2018. Oryginalność/wartość: wartość uzyskanych wyników zwiększa ich unikalność, gdyż zmiany efektywności hedgingu delta na polskim rynku opcji nie są poruszane w literaturze przez innych autorów.
Źródło:
Problemy Zarządzania; 2020, 4/2020 (90); 163-177
1644-9584
Pojawia się w:
Problemy Zarządzania
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Trend of arsenic pollution and subsequent bioaccumulation in Oryza sativa and Corchorus capsularis in Bengal Delta
Autorzy:
Bhattacharya, S.
Guha, G.
Gupta, K.
Chattopadhyay, D.
Mukhopadhyay, A.
Ghosh, U.C.
Powiązania:
https://bibliotekanauki.pl/articles/10831.pdf
Data publikacji:
2014
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
trend
arsenic pollution
bioaccumulation
rice
Oryza sativa
jute
Corchorus capsularis
Bengal Delta zob.Ganges Delta
Ganges River
Ganges Delta
Opis:
Oryza sativa Linn. (rice) and Corchorus capsularis Linn. (jute) are the two major crops of the Bengal basin. Both rice and jute are generally grown in submerged flooded conditions, where arsenic bioavailability is high in soil. The consumers of the edible parts from both plants therefore face an inevitable source of exposure to arsenic, with consequent accumulation and toxicity. The objective of the study was to observe the in-vivo temporal variation of arsenic bioaccumulation in the different parts of O. sativa and C. capsularis. Rice plant specimens (Aman rice, Ratna variety) of different age groups (1, 2 and 3 months old) were analyzed in HG-AAS for absorbed arsenic content in different parts. The accumulation of arsenic remained significantly high in the initial phase of growth, but decreased with time. Amount of arsenic bioaccumulation followed the decreasing order: root > basal stem > median stem > apical stem > leaves > grains in all the three age groups of the rice plant samples. C. capsularis followed a trend of arsenic bioaccumulation similar to O. sativa. O. sativa had more accumulation potential than C. capsularis, but C. capsularis showed much higher efficiency of arsenic translocation in the above ground parts. This is the first ever report of time-dependent decrease in arsenic bioaccumulation in O. sativa and C. capsularis. The contamination level can reach the grain part in significant amount and can cause health hazards in more severely arsenic affected areas. Intensive investigation on a complete food chain is urgently needed in the arsenic contaminated zones for further risk assessments.
Źródło:
International Letters of Natural Sciences; 2014, 16
2300-9675
Pojawia się w:
International Letters of Natural Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Synchronization of transmission systems with ANS-DM codecs
Autorzy:
Godek, Juliusz
Golański, Ryszard
Powiązania:
https://bibliotekanauki.pl/articles/2014241.pdf
Data publikacji:
2021
Wydawca:
Państwowa Wyższa Szkoła Zawodowa w Tarnowie
Tematy:
delta modulation
non-uniform sampling
Adaptive Delta Modulation with Non-uniform Sampling (ANS-DM)
ANS-DM
digital PLL
digital transmission
one-bit codec delta
modulacja delta
nierównomierne próbkowanie
cyfrowy PLL
transmisja cyfrowa
jednobitowy kodek delta
Opis:
Adaptive Delta Modulation with Non-uniform Sampling (ANS-DM) is one of the waveform coding techniques, where a sampling instant and a quantization step size are adapted to the signal. The ANS-DM modulator produces an output binary stream, that carries information about the signal and includes necessary data of coder parameters (sampling instant and quantization step). In the demodulator, these values are recovered for proper signal reconstruction. The paper reports the problem of synchronizing clocks (transmitting and receiving) in the (ANS-DM) delta codecs systems. The original synchronization method, valuable in systems dedicated to the transmission of the bits with variable time duration was projected and experimentally verified. Performed measurements and observations have shown the elimination of the synchronization loss phenomenon.
Źródło:
Science, Technology and Innovation; 2021, 12, 1; 37-44
2544-9125
Pojawia się w:
Science, Technology and Innovation
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Proces pomiaru w przetworniku A/C typu Sigma-Delta
Measurement process in Sigma-Delta AD converter
Autorzy:
Jakubiec, J.
Powiązania:
https://bibliotekanauki.pl/articles/152012.pdf
Data publikacji:
2008
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
przetwornik Sigma-Delta
kwantowanie
błąd pomiaru
sigma-delta converter
quantization
measurement error
Opis:
Działania realizowane przez przetwornik A/C typu Sigma-Delta opisano w artykule jako proces pomiaru podzielony na trzy etapy: przetwarzanie analogowe, kwantowanie i przetwarzanie cyfrowe. Poddano analizie podstawowe źródła błędu, a następnie określono wpływ decymacji i filtracji na właściwości wypadkowego błędu wyniku pomiaru. Rozważania analityczne zilustrowano wynikami symulacji uzyskanymi przy użyciu metody Monte Carlo.
A basic scheme of a Sigma-Delta AD converter, analyzed in the paper, is shown in Fig. 1. The converter performs a quantization process, which can be described as compensation of the charge, delivered to the integrator from the source of the measured voltage Ux, with quanta of charge obtained synchronously with clock CLK when the switch P is closed. Value of a charge quantum is given by Eq. (1) and the balance state of the quantizer by Eq. (2). Basing on this equation one can obtain expression (3) describing a measurement result and Eq. (4) that describes value of a voltage quantum. All stages of the processing made by Sigma-Delta converter, i.e. analog conversion, quantization and digital processing, are shown in Fig. 3. One can distinguish three main error sources in this process - input error described by Eq. (6) and two errors connected with quantization: quantization error and standard error caused by dispersion of the quanta values (Eqs. (8), (9) and Fig. 3). Next considerations deal with analysis of decimation and averaging influence on the quantization error and the standard error. Fig. 4 shows exemplary histogram of the quantization error after averaging and Fig. 5 the error being the result of composition of both mentioned errors. Having the errors described one can calculate uncertainty of a measurement result using the procedure presented in paper [3].
Źródło:
Pomiary Automatyka Kontrola; 2008, R. 54, nr 6, 6; 343-346
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Argument Increment Stability Criterion for Linear Delta Models
Autorzy:
Hofreiter, M.
Zitek, P.
Powiązania:
https://bibliotekanauki.pl/articles/908101.pdf
Data publikacji:
2003
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
automatyka
delta model
stability criterion
conformal mapping
delta operator
argument increment rule
Opis:
Currently used stability criteria for linear sampled-data systems refer to the standard linear difference equation form of the system model. This paper presents a stability criterion based on the argument increment rule modified for the delta operator form of the sampled-data model. For the asymptotic stability of this system form it is necessary and sufficient that the roots of the appropriate characteristic equation lie inside a circle in the left half of the complex plane, the radius of which is inversely proportional to the sampling period. Therefore the argument increment of the system characteristic polynomial of an asymptotically stable delta model has to increase by 2pi n if this circle has been run around in the counter-clockwise direction. The criterion developed based on this principle permits not only the proof of the system stability itself, but also the approximation of the dominant roots of its characteristic equation.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2003, 13, 4; 485-491
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Charakterystyka zbiorowisk roślinnych z udziałem słonorośli oraz ich ochrona na obszarze wstecznej delty Świny
Characteristic of salt plant community and its protection on the area of retrograde of Swina river delt
Autorzy:
Czyż, H.
Kitczak, T.
Durkowski, T.
Powiązania:
https://bibliotekanauki.pl/articles/1819671.pdf
Data publikacji:
2010
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
delta Świny
zbiorowisko roślinne
słonorośle
środowisko naturalne
Delta Swiny
plant community
environment
Opis:
Zbiorowiska halofilne są dość rzadkie na terenie Polski i to nie tylko na terenach śródlądowych, ale także i na nadmorskich, choć sama flora słonorośli naszego kraju jest dość bogato reprezentowana [14]. W świetle badań [10, 11, 15, 17, 19] nisko położone, podmokłe gleby, zwłaszcza organiczne, wykazują najbardziej sprzyjające warunki do rozwoju roślinności słonolubnej. Bogate i dobrze wykształcone zbiorowiska z udziałem słonorośli występują na wyspach Wolin i Uznam, u ujścia Regi oraz nad Zatoką Pucką [2]. Ciekawe zbiorowiska halofilne występują na wyspie Karsiborska Kępa [18]. Zbiorowiska tej roślinności, zdaniem Piotrowskiej [15, 16] są najbardziej wykształcone we wstecznej delcie Świny, gdzie sięgają nawet kilku kilometrów w głąb lądu. Zdaniem tej autorki rozmieszczenie słonorośli wzdłuż linii brzegowej morza nie przekracza linii Wisły. Celem przeprowadzonych badań było określenie składu florystycznego, wartości użytkowej i walorów przyrodniczych zbiorowisk roślinnych z udziałem halofitów oraz możliwości ich ochrony w warunkach siedliskowych wstecznej delty Świny.
Scientific research was realized on the Karsiborska Kypa Island, which is one of the biggest islands laid in the retrograde delta of Swina river. Research was conducted on the meadow-pasture community area. After the preliminary analysis, grasslands located on the mineral-rot and mud-rot soils were chosen to the detailed analysis. They were conducted using botanical-weight method. Location of research sites is shown in Figure 1. Utility value of individual sward communities was determined on the basis of the utility (Lwu) - [8], and natural values by valorisation numbers (Lwp) - [13]. Configuration of ground water level was determined using piezometers, which were deployed in the area covered by the research (Fig. 1). In the term of first cut, on the allowed areas, plant samples were taken to the floristic botanical analyses. Use value of the grassland, was define by number of use value and natural value was define by number of valorization. Water level was detected by piezometres, which were located on the research areas. Differential environmental conditions influenced the community area. On the mineral-rot soil, community of: Agrostis stolonifera, Elymus repens with Festuca rubra, Agrostis stolonifera with Deschampsia caespitosa were formed. On the mud-rot soil with the higher level of groundwater, community of: Juncus gerardi and Festuca rubra with Juncus gerardi were formed. Little occurrence of salt plants (Juncus gerardi, Triglochin maritimum, Glaux maritime, Triglochin palustris,Plantago maritima and Lotus tenuis and Trifolium fragiferum) justified extensive pasture farming or mowing, which provided active environmental protection for salt plants, and also take notice on the necessary of efficient running of reclamation inftastructure. In order to maintain stability of humidity conditions on and the prevalence of communities of meadow-pasture with halophytes on Karsiborska Kepa it is necessary to improve functioning of the drainage infrastructure, with the possibility of regulation of groundwater level in various parts of the island and to stabilize agricultural use of grasslands by rational economy of grassland.
Źródło:
Rocznik Ochrona Środowiska; 2010, Tom 12; 119-125
1506-218X
Pojawia się w:
Rocznik Ochrona Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stratigraphy and sedimentology of the Niger Delta
Autorzy:
Reijers, T. J. A.
Powiązania:
https://bibliotekanauki.pl/articles/94623.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet im. Adama Mickiewicza w Poznaniu
Tematy:
Niger Delta
biostratigraphy
sedimentology
(mega)sequences
cycles
Delta Nigru
biostratygrafia
sedymentologia
cykle
Opis:
During the Cenozoic, until the Middle Miocene, the Niger Delta grew through pulses of sedimentation over an oceanward-dipping continental basement into the Gulf of Guinea; thereafter progradation took place over a landward-dipping oceanic basement. A 12,000 m thick succession of overall regressive, of flapping sediments resulted that is composed of three diachronous siliciclastic units: the deep-marine pro-delta Akata Group, the shallow-marine delta-front Agbada Group and the continental, delta-top Benin Group. Regionally, sediment dispersal was controlled by marine transgressive/regressive cycles related to eustatic sea-level changes with varying duration. Differential subsidence locally influenced sediment accumulation. Collectively, these controls resulted in eleven chronostratigraphically confined delta-wide megasequences with considerable internal lithological variation. The various sea-level cycles were in or out of phase with each other and with local subsidence, and interfered with each other and thus influenced the depositional processes. At the high inflection points of the long-term eustatic sea-level curve, floodings took place that resulted in delta-wide shale markers. At the low inflection points, erosional channels were formed that are often associated, downdip, with turbidites in low-stand sediments (LSTs). The megasequences contain regional transgressive claystone units (TST) followed by a range of heterogeneous fine-to-coarse progradational or aggradational siliciclastic (para)sequence sets formed during sea-level high-stand (HST). An updated biostratigraphic scheme for the Niger Delta is presented. It also updates a sedimentation model that takes into consideration local and delta-wide effects of sea-level cyclicity and delta tectonics. Megasequences were formed over time intervals of ~5 Ma within individual accurate megastructures that laterally linked into depobelts. The megasequences form the time-stratigraphic frame of the delta and are the backbone for the new delta-wide lithostratigraphy proposed here. Such a new lithostratigraphy is badly needed, in particular because of the vigorous new activity in the offshore part of the Niger Delta (not covered in this contribution). There, as well as in the onshore part of the delta, the traditional lithostratigraphic subdivision of the Cenozoic Niger Delta section into three formations is insufficient for optimum stratigraphic application; moreover, the various informal subdivisions that have been proposed over time are inconsistent.
Źródło:
Geologos; 2011, 17, 3; 133-162
1426-8981
2080-6574
Pojawia się w:
Geologos
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Eustatic and tectonic control on late Eocene fan delta development (Orava Basin, Central Western Carpathians)
Autorzy:
Starek, D.
Sliva, L’.
Vojtko, R.
Powiązania:
https://bibliotekanauki.pl/articles/2058980.pdf
Data publikacji:
2012
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Paleogene
Orava
Western Carpathians
fan delta
mass flow deposits
coarse-grained delta
Opis:
The evolution of the Central Carpathian Paleogene Basin (CCPB) reflects an important role of relative sea level changes on a tectonically active basin margin. After the initial upper Lutetian/Bartonian transgression, the next regressive-transgressive cycle played a key role in a formation of the late Eocene fan delta facies associations in the southern Orava region of Northern Slovakia. Detailed sedimentary analysis allowed the separation of the following three facies associations which represent distinct depositional environments: alluvial fan (subaerial fan delta; Unit 1); subaqueous fan delta (Unit 2); and prodelta/slope and basin (Unit 3). The first stage of delta development is connected with eustatic sea level fall at the Bartonian/Priabonian boundary, accompanied by subaerial exposure, fluvial incision and deposition of alluvial fan sediments. Subaerial deposition was characterized by a variety of mass flow conglomerates with a red muddy matrix, interfingering with stream or sheetflood deposits. The next stage of the delta corresponds to high-amplitude transgression related to rapid tectonic subsidence along the CCPB margins during the Priabonian. The vertical arrangement of facies suggests retrograde delta development that shows rapid submergence of the subaerial parts and onlap of subaqueous mass flow conglomerates, often reworked by waves or wave-induced shallow-marine currents. Continuous deepening of the depositional environment during the late Priabonian/early Rupelian led to the relatively rapid superposition of prodelta/slope and basin facies associations by slowly accumulated hemipelagic deposis.
Źródło:
Geological Quarterly; 2012, 56, 1; 67-84
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 204

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