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Wyszukujesz frazę "Chakraborty, K." wg kryterium: Autor

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    Tytuł:
    Solutions of cubic equations in quadratic fields
    Autorzy:
    Chakraborty, K.
    Kulkarni, Manisha
    Powiązania:
    https://bibliotekanauki.pl/articles/1390522.pdf
    Data publikacji:
    1999
    Wydawca:
    Polska Akademia Nauk. Instytut Matematyczny PAN
    Tematy:
    elliptic curves
    Diophantine equation
    Opis:
    Let K be any quadratic field with $_K$ its ring of integers. We study the solutions of cubic equations, which represent elliptic curves defined over ℚ, in quadratic fields and prove some interesting results regarding the solutions by using elementary tools. As an application we consider the Diophantine equation r+s+t = rst = 1 in $_K$. This Diophantine equation gives an elliptic curve defined over ℚ with finite Mordell-Weil group. Using our study of the solutions of cubic equations in quadratic fields we present a simple proof of the fact that except for the ring of integers of ℚ(i) and ℚ(√2), this Diophantine equation is not solvable in the ring of integers of any other quadratic fields, which is already proved in [4].
    Źródło:
    Acta Arithmetica; 1999, 89, 1; 37-43
    0065-1036
    Pojawia się w:
    Acta Arithmetica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Soil temperature prediction from air temperature for alluvial soils in lower Indo-Gangetic plain
    Autorzy:
    Barman, D.
    Kundu, D.K.
    Pal, S.
    Chakraborty, A.K.
    Jha, A.K.
    Mazumdar, S.P.
    Saha, R.
    Bhattacharyya, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/25358.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Instytut Agrofizyki PAN
    Opis:
    Soil temperature is an important factor in biogeochemical processes. On-site monitoring of soil temperature is limited in spatio-temporal scale as compared to air temperature data inventories due to various management difficulties. Therefore, empirical models were developed by taking 30-year long-term (1985-2014) air and soil temperature data for prediction of soil temperatures at three depths (5, 15, 30 cm) in morning (0636 Indian standard time) and afternoon (1336 Indian standard time) for alluvial soils in lower Indo-Gangetic plain. At 5 cm depth, power and exponential regression models were best fitted for daily data in morning and afternoon, respectively, but it was reverse at 15 cm. However, at 30 cm, exponential models were best fitted for both the times. Regression analysis revealed that in morning for all three depths and in afternoon for 30 cm depth, soil temperatures (daily, weekly, and monthly) could be predicted more efficiently with the help of corresponding mean air temperature than that of maximum and minimum. However, in afternoon, prediction of soil temperature at 5 and 15 cm depths were more precised for all the time intervals when maximum air temperature was used, except for weekly soil temperature at 15 cm, where the use of mean air temperature gave better prediction.
    Źródło:
    International Agrophysics; 2017, 31, 1
    0236-8722
    Pojawia się w:
    International Agrophysics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Barriers in the Advancement of Solar Energy in Developing Countries like India
    Bariery w rozwoju energii słonecznej w krajach rozwijających się na przykładzie Indii
    Autorzy:
    Chakraborty, S.
    Sadhu, P. K.
    Goswami, U.
    Powiązania:
    https://bibliotekanauki.pl/articles/371096.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Komitet Człowiek i Środowisko PAN
    Tematy:
    solar energy
    solar market
    renewable energy
    energia słoneczna
    rynek energii solarnej
    energia odnawialna
    Opis:
    The present paper puts an emphasis on the current energy market scenario and different types of barriers associated with the advancement of solar energy in a developing countries like India. Solar energy, best suited for urban environment, can be housed in a limited space and is characterized as a pollution free, environmentally friendly, as well as noise-free source of electricity. Among the available renewable energies, solar energy is considered to be an integral one, owing to its reduction in cost at an exponential rate day-by-day. The present study deals with the potential of solar energy market in the Indian subcontinent along with several other problems that it needs to overcome in order to be established as an independent system.
    Artykuł omawia scenariusze związane ze współczesnym rynkiem energetycznym, wskazując na różnorodne typy barier, na które napotyka rozwój energii solarnej w krajach rozwijających się, takich jak Indie. Energia słoneczna doskonale sprawdza się w warunkach miejskich, przeznaczone do jej pozyskiwania instalacje nie potrzebują dużo miejsca i nie zanieczyszczają powietrza, a ponadto nie emitują hałasu. Wśród różnorodnych źródeł energii to właśnie energia solarna wydaje się być najbardziej korzystna, biorąc pod uwagę jej nieustannie malejące koszty. Niniejsza praca przedstawia potencjał rozwoju rynku energii słonecznej w Indiach, zwracając szczególna uwagę na problemy, które należy rozwiązać, aby mógł on funkcjonować, jako niezależny system.
    Źródło:
    Problemy Ekorozwoju; 2016, 11, 2; 75-80
    1895-6912
    Pojawia się w:
    Problemy Ekorozwoju
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Measurement of radioactive impact of the gas well accident on environment of Sylhet division in Bangladesh
    Autorzy:
    Chakraborty, S. R.
    Saha, K. K.
    Rahman, A. K. M. R.
    Kamal, M.
    Chowdhury, M. I.
    Alam, Md. K.
    Powiązania:
    https://bibliotekanauki.pl/articles/411611.pdf
    Data publikacji:
    2013
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Natural gas well accident
    Environmental radioactivity
    Public exposure etc
    Opis:
    The main goal of this study is to carry out the public exposure contribution from radioactive materials occurring due to the accident of natural gas exploration well of Sylhet division in Bangladesh. This study has been performed by using a gamma spectrometry of Genie 2000 software embedded PC-based High Purity Germanium (HPGe) detector system. The measured activity concentrations of naturally occurring radionuclides 232Th, 226Ra, and 40K have been in the public safety limit on the environment of the study areas. The specific activity of detected anthropogenic radionuclide 137Cs has been found to be very little with a mean value of 1.65 ± 0.61 and 1.13 ± 0.57 Bq•kg–1 in the Magurchhera and Haripur gas field area respectively.
    Źródło:
    International Letters of Chemistry, Physics and Astronomy; 2013, 9, 1; 48-60
    2299-3843
    Pojawia się w:
    International Letters of Chemistry, Physics and Astronomy
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Early Pliocene calcareous and siliceous microfossils of the Sawai Bay Formation, Car Nicobar Island, northern Indian Ocean
    Autorzy:
    Chakraborty, Arindam
    Ghosh, Amit K.
    Mccartney, Kevin
    Saxena, Stuti
    Dey, Rikee
    Roy, Lopamudra
    Powiązania:
    https://bibliotekanauki.pl/articles/1835597.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    Zanclean
    calcareous nannofossils
    radiolarians
    diatoms
    silicoflagellates
    sponge spicules
    Andaman islands
    Nicobar islands
    India
    nanoplankton wapienny
    radiolarie
    okrzemki
    wyspy Andaman
    wyspy Nicobar
    Indie
    Opis:
    The present contribution provides a study of calcareous nannofossils and siliceous microfossils from the Sawai Bay Formation on Car Nicobar Island, northern Indian Ocean. Two stratigraphically short sediment intervals near Sawai Bay have been examined. Qualitative and quantitative microfossil analyses show the Sawai Bay ‘A’ Section to be devoid of siliceous microfossils, while 24 well-preserved calcareous nannofossil taxa are identified. The Sawai Bay ‘B’ Section yields 18 calcareous nannofossil, 33 radiolarian and 25 diatom taxa. The calcareous nannofossil index taxa (Ceratolithus armatus Müller, 1974a and C. cristatus Kamptner, 1950) indicate both sections to be from zones NN12 (CN10b) and NN13 (CN10c) of early Pliocene (Zanclean) age. The radiolarian taxa, i.e., Didymocyrtis avita Riedel, 1953, Euchitonia spp., Siphocampe lineata (Ehrenberg) Nigrini, 1977, Stichocorys peregrina Riedel, 1953, Semantis spp. and Stylochlamydium sp. are common in the Sawai Bay ‘B’ Section, which is assigned to Zone RN9. Most of the diatom taxa are represented by rep-resentatives of the genera Actinocyclus Ehrenberg, 1837, Azpeitia Peragallo in Tèmpere and Peragallo, 1912, Coscinodiscus Ehrenberg, 1839a, Grammatophora Ehrenberg, 1841 and Triceratium Ehrenberg, 1839b, with the benthic diatom species Triceratium favus Ehrenberg, 1839b being predominant (~35% of the total diatom count). Siliceous microfossils are also represented by silicoflagellates dominated by Dictyocha spp. and sponge spicules dominated by astrophorids.
    Źródło:
    Acta Geologica Polonica; 2021, 71, 2; 175-198
    0001-5709
    Pojawia się w:
    Acta Geologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of organic inputs on strength and stability of soil aggregates under rice-wheat rotation
    Autorzy:
    Das, B.
    Chakraborty, D.
    Singh, V.K.
    Aggarwal, P.
    Singh, R.
    Dwivedi, B.S.
    Powiązania:
    https://bibliotekanauki.pl/articles/25472.pdf
    Data publikacji:
    2014
    Wydawca:
    Polska Akademia Nauk. Instytut Agrofizyki PAN
    Tematy:
    tensile strength
    stability
    soil aggregate
    rice
    wheat
    cereal crop rotation
    Opis:
    The study aims to elucidate the impact of organic inputs on strength and structural stability of aggregates in a sandy loam soil. Tensile strength, friability and water stability of aggregates, and the carbon contents in bulk soil and in large macro (>2 mm), small macro (0.25-2 mm), micro (0.053-0.25 mm) and silt+clay size (<0.053) aggregates were evaluated in soils from a long-term experiment with rice-wheat rotation at Modipuram, India, with different sources and amounts of organic C inputs as partial substitution of N fertilizer. Addition of organic substrates significantly improved soil organic C contents, but the type and source of inputs had different impacts. Tensile strength of aggregates decreased and friability increased through organic inputs, with a maximum effect under green gram residue (rice)-farmyard manure (wheat) substitution. Higher macroaggregates in the crop residue- and farmyard manure-treated soils resulted in a higher aggregate mean weight diameter, which also had higher soil organic C contents. The bulk soil organic C had a strong relation with the mean weight diameter of aggregates, but the soil organic C content in all aggregate fractions was not necessarily effective for aggregate stability. The soil organic C content in large macroaggregates (2-8 mm) had a significant positive effect on aggregate stability, although a reverse effect was observed for aggregates <0.25 mm. Partial substitution of nitrogen by organic substrates improved aggregate properties and the soil organic C content in bulk soil and aggregate fractions, although the relative effect varied with the source and amount of the organic inputs.
    Źródło:
    International Agrophysics; 2014, 28, 2
    0236-8722
    Pojawia się w:
    International Agrophysics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Identifying overlapping phylogenetic and geographic roots of HIV - 1 evolution through computational analyses
    Autorzy:
    Singh, P.K.
    Banik, R.
    Chakraborty, H.J.
    Das, S.G.
    Ganguli, S.
    Datta, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/11359.pdf
    Data publikacji:
    2014
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    phylogenetic root
    geographic root
    evolution
    computational analysis
    HIV-1
    genome
    recombinant strain
    AIDS
    human disease
    acquired immunodeficiency syndrome zob.AIDS
    acquired immune deficiency syndrome zob.AIDS
    Opis:
    HIV-1 or Human Immuno Deficiency Virus-1 is the main causative agent of Acquired Immuno Deficiency Syndrome (AIDS). Human host infected with HIV - 1 extensively harbours many viral variants but very little is known about the difference in pattern[17] of evolution of phylogenetic lineages of HIV-1 non recombinant, normal inter subtype recombinant and main two specific recombinant forms of HIV-1 i.e., Circulating Recombinant Forms (CRFs) and Unique Recombinant Forms (URFs). This study is mainly concerned with study of the difference in evolutionary lineages of non-recombinant and recombinant sequences of HIV-1 genome sequences and identification of geographically rich areas which has reported high degree of HIV-1 occurrence and variety. Total 1550 HIV-1 genome sequences were obtained from HIV Los Alamos Database. The sequences were aligned using MAFFT (Multiple Alignment using Fast Fourier Transform) web server tool. Alignment was carried out using 10 different set of alignment parameter values. After alignment the aligned file was used for constructing N-J phylogenetic tree using Clustal X2 tool. Phylogenetic analysis was performed keeping in mind the category to which the sequence belongs. Upon analysis it was observed that the clade containing the probable ancestor belongs remained constant in all cases of different alignment values. Non recombinant isolates, inter subtype recombinants, CRFs, URFs all followed different patterns of evolution. Non recombinant sequences were found geographically specific and subtype specific to some extent whereas, normal recombinants were subtype specific and less geographically specific. CRFs showed variation among the pattern of their evolution. At some instances the sequences occurred as sister taxa of non-recombinant or normal inter subtype recombinant sequences, while at some instances as sister taxa of other CRFs where they were geographically specific. Three CRFs existed as completely diverged sequences. URFs were four in number; two of them were Indian isolates of while other two were Japanese isolates. URFs were found to be totally geographically specific. Geography wise high rate of variation was observed in India and Japan as these two countries had sequences belonging to all of the above categories. Cameroon and South Africa have very large number isolates and a considerable amount of genetic variation among isolates but they lack URFs.
    Źródło:
    International Letters of Natural Sciences; 2014, 02
    2300-9675
    Pojawia się w:
    International Letters of Natural Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Optimal selection of dental implant for different bone conditions based on the mechanical response
    Autorzy:
    Roy, S.
    Das, M.
    Chakraborty, P.
    Biswas, J. K.
    Chatterjee, S.
    Khutia, N.
    Saha, S.
    Roychowdhury, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/307549.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    wytrzymałość kości
    implanty stomatologiczne
    analiza FEM
    pacjent
    bone condition
    porous dental implant
    FE Analysis
    patient specific
    Opis:
    Bone quality varies from one patient to another extensively; also, Young’s modulus may deviate up to 40% of normal bone quality, which results into alteration of bone stiffness immensely. The prime goal of this study is to design the optimum dental implant considering the mechanical response at bone implant interfaces for a patient with specific bone quality. Method. 3D model of mandible and natural molar tooth were prepared from CT scan data while, dental implants were modelled using different diameter, length and porosity and FE analysis was carried out. Based on the variation in bone density, five different bone qualities were considered. First, failure analysis of implants, under maximum biting force of 250N had been performed; next, the implants, those survived were selected for observing the mechanical response at bone implant interfaces under common chewing load of 120N. Result. Maximum Von Mises stress did not surpass the yield strength of the implant material (TiAl4V). However, factor of safety of 1.5 was considered and all but two dental implants survived the design stress or allowable stress. Under 120N load, distribution of Von Mises stress and strain at the bone-implant interface corresponding to the rest of the implants for five bone conditions were obtained and enlisted. Conclusion. Implants, exhibiting interface strain within 1500-3000 microstrain range show the best bone remodelling and osseointegration. So, implant models, having this range of interface strains were selected corresponding to the particular bone quality. A set of optimum dental implants for each of the bone qualities were predicted.
    Źródło:
    Acta of Bioengineering and Biomechanics; 2017, 19, 2; 11-20
    1509-409X
    2450-6303
    Pojawia się w:
    Acta of Bioengineering and Biomechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Charged Excitons in the Quantum Hall Regime
    Autorzy:
    Schüller, C.
    Broocks, K.-B.
    Schröter, P.
    Heyn, C.
    Heitmann, D.
    Bichler, M.
    Wegscheider, W.
    Apalkov, V. M.
    Chakraborty, T.
    Powiązania:
    https://bibliotekanauki.pl/articles/2038336.pdf
    Data publikacji:
    2004-09
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    71.35.-y
    71.30.+h
    71.35.Ji
    71.70.Ej
    Opis:
    We review our recent optical experiments on two-dimensional electron systems at temperatures below 1 K and under high magnetic fields. The two-dimensional electron systems are realized in modulation-doped GaAs-AlGaAs single quantum wells. Via gate electrodes the carrier density of the two-dimensional electron systems can be tuned in a quite broad range between about 1×10$\text{}^{10}$ cm$\text{}^{-2}$ and 2×10$\text{}^{11}$ cm$\text{}^{-2}$. In dilute two-dimensional electron systems, at very low electron densities, we observe the formation of negatively charged excitons in photoluminescence experiments. In this contribution we report about the observation of a dark triplet exciton, which is observable at temperatures below 1 K and for electron filling factors <1/3, i.e., in the fractional quantum Hall regime only. In experiments where we have increased the density of the two-dimensional electron systems so that a uniform two-dimensional electron system starts to form, we have found a strong energy anomaly of the charged excitons in the vicinity of filling factor 1/3. This anomaly was found to exist in a very narrow parameter range of the density and temperature, only. We propose a model where we assume that localized charged excitons and a uniform Laughlin liquid coexist. The localized charged exciton in close proximity to the Laughlin liquid leads to the creation of a fractionally-charged quasihole in the liquid, which can account for the experimentally observed anomaly.
    Źródło:
    Acta Physica Polonica A; 2004, 106, 3; 341-353
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Assessment of Radiological Dose around a 3-MW TRIGA Mark-II Research Reactor
    Autorzy:
    Rahman, A. F. M. M.
    Shamsuzzaman, M.
    Rahman, M. S.
    Uddin, K.
    Yeasmin, S.
    Nazmul, Haque H. M.
    Akramuzzaman, M. M.
    Chakraborty, S. R
    Powiązania:
    https://bibliotekanauki.pl/articles/412377.pdf
    Data publikacji:
    2013
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    source term
    release rate
    TRIGA Mark-II reactor
    dispersion
    ingestion and deposition of radionuclide
    Gaussian plume model
    dose calculations
    Opis:
    A hypothetical accidental case of a 3-MW TRIGA Mark-II research reactor has been assumed to assess the radiological consequences due to the deposition of 137Cs and 90Sr on ground, vegetation, milk and meat. The air concentrations in sixteen cardinal directions have been estimated where the maximum concentration has been found to be at 110 m distance from the core of the reactor for all the directions. Calculated maximum doses of 137Cs, 90Sr and both 137Cs and 90Sr have been found to be within the ranges of 0.005-0.014 μSv hr–1, 0.013-0.036 μSv hr–1 and 0.018-0.05 μSv hr–1, respectively for all the directions, which are below the measured background dose limit 0.25 μSv hr–1 and also within the IAEA acceptable dose rate limit of 0.5 μSv hr–1. The calculated low doses due to the aforementioned radionuclides can be considered negligible with regard to the radiation hazards. The relationship between total effective dose rate for various pathways (i.e. immersion, inhalation, ground deposition, and ingestion of contaminated vegetation, milk, meat) and air concentration in all the directions has been established. Obtained relation reveals that the total effective dose rate is directly proportional to the air concentration, and the overall proportionality constants for 137Cs and 90Sr radionuclides have been obtained as 0.57 and 0.28, respectively. This study might provide information on the radiological safety required for the radiation protection purposes of the people living in the vicinity of the reactor site.
    Źródło:
    International Letters of Chemistry, Physics and Astronomy; 2013, 10, 2; 183-200
    2299-3843
    Pojawia się w:
    International Letters of Chemistry, Physics and Astronomy
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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