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Wyświetlanie 1-15 z 55
Tytuł:
Health risk assessment of heavy metals in irrigation water, soil and vegetables from different farms in Riyadh district, Saudi Arabia
Autorzy:
Alturiqi, A.S.
Albedair, L.A.
Ali, M.H.H.
Powiązania:
https://bibliotekanauki.pl/articles/1192504.pdf
Data publikacji:
2020
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie / Polskie Towarzystwo Magnezologiczne im. Prof. Juliana Aleksandrowicza
Tematy:
heavy metal
vegetables
dietary intake
health risk
HQ
THQ
ILCR
Opis:
The safety and security of different foodstuffs are considered important and have a high priority in global sustainable development. The contents of Fe, Mn, Cu, Zn, Ni, Pb and Cd were estimated in edible parts of 60 vegetable samples, irrigation water and agricultural soil collected from 5 farms in suburban areas around Riyadh district, Saudi Arabia. Also, soil pollution indices, pollution load index and contamination factor (PLI, CF), bioaccumulation factor (BAF), non-carcinogenic and carcinogenic risk indices (HQ, THQ, and ILCR) were estimated. The content of heavy metals in irrigation water and soil was within the recommended permissible levels, except for Cd in soil, which exceeds permissible levels. The trend of metal concentrations in both agricultural soil and vegetables was found in the order: Fe > Mn > Zn > Cu > Ni > Pb > Cd. Cluster analysis of the metal content in vegetables showed a tendency towards the accumulation of heavy metals in the order of leaves > roots > fruits > flowers > tuber. The BAFs values found were < 1.0, HQs values for Fe, Mn, Cu, Zn and Ni were found to be < 1, while the estimated HQs for Pb and Cd were > 1, posing greater risk to the health of adults and children. THQ values were higher for children compared to adults. ILCR values for Cd showed a serious issue, as it exceeds the threshold risk limit (>10−4) in all parts of the investigated vegetables in all sampling sites.
Źródło:
Journal of Elementology; 2020, 25, 4; 1269-1289
1644-2296
Pojawia się w:
Journal of Elementology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Case Study of Diffusion of Innovation under Competition
Autorzy:
Gündüç, S.
Powiązania:
https://bibliotekanauki.pl/articles/1029620.pdf
Data publikacji:
2018-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
PACS/topics:02.30.Hq
02.60.Cb
89.65.Gh
Opis:
In this work, the aim is to discuss the relative importance of the driving parameters of the diffusion of innovation under competition. As a case study the competitive existence of Android and iOS operating systems are modeled in the context of an extended Bass model. The chosen model consists of two coupled differential equations. Each differential equation has the same form of the well known Bass equation with an extra term which represents the effect of the existence of the competitor. Since the smartphone sales and usage are globally well documented, publicly available global smartphone market share and sales data are used to determine the model parameter values. The smartphone global market share data spans 28 quarters starting from the first quarter of 2009. The distribution of the market share in the first quarter has been used as the initial values of the competing operating systems. A minimization process obtains the free parameters (six in total) of the differential equations. The values of the parameters are fixed by minimizing the difference between the solution of Bass equation and the smartphone global market share data. The parameter values of iOS and Android operating systems indicate that, on the worldwide scale, the adaptation of new ideas/products the dominantly led by the personal interactions. In fact, through social networks, information flow is immense, and individuals rely on the information obtained directly from a trusted individual. Publicity parameter values indicate that very rarely decision of an individual is formed by only the mass media or publicity. On the contrary, to the publicity parameter, it is observed that the existence of a competitor has a considerable effect on the sales of both parties.
Źródło:
Acta Physica Polonica A; 2018, 133, 6; 1465-1469
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Solution of a Class of Optimization Problems Based on Hyperbolic Penalty Dynamic Framework
Autorzy:
Evirgen, F.
Powiązania:
https://bibliotekanauki.pl/articles/1031640.pdf
Data publikacji:
2017-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
02.60.Pn
02.70.-c
02.30.Hq
Opis:
In this study, a gradient-based dynamic system is constructed in order to solve a certain class of optimization problems. For this purpose, the hyperbolic penalty function is used. Firstly, the constrained optimization problem is replaced with an equivalent unconstrained optimization problem via the hyperbolic penalty function. Thereafter, the nonlinear dynamic model is defined by using the derivative of the unconstrained optimization problem with respect to decision variables. To solve the resulting differential system, a steepest descent search technique is used. Finally, some numerical examples are presented for illustrating the performance of the nonlinear hyperbolic penalty dynamic system.
Źródło:
Acta Physica Polonica A; 2017, 132, 3; 1062-1065
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermal Development of Free Volumes in Nafion Membrane
Autorzy:
Melikhova, O.
Čížek, J.
Košinová, L.
Hruška, P.
Powiązania:
https://bibliotekanauki.pl/articles/1033913.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.66.Hq
82.35.Lr
Opis:
In this work we employed positron lifetime spectroscopy for investigation of the thermal development of free volumes in H⁺ Nafion membrane over a broad range of temperatures from -150 to 150°C. Positron lifetime studies were combined with differential scanning calorimetry. Size distribution of free volumes was determined from ortho-positronium contribution to positron lifetime spectra. Our investigations revealed that the mean size of free volume holes strongly increases with temperature. On the other hand, the width of the size distribution and the positronium yield decreases with temperature. Transition temperatures corresponding to a change in the slope of the temperature dependence of ortho-positronium lifetime were identified. Results of positron lifetime spectroscopy agree well with the curve obtained by differential scanning calorimetry.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1538-1542
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Elastic Properties of Colossal Magnetoresistive Manganites $R_{0.67} Sr_{0.33} Mn O_3$ (R = Pr, Nd, Gd)
Autorzy:
Reddy, Y.
Powiązania:
https://bibliotekanauki.pl/articles/1398673.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.47.Gk
75.47.Lx
62.20.de
43.20.Hq
Opis:
The polycrystalline bulk samples of $R_{0.67} Sr_{0.33} Mn O_3$ (R = Pr, Nd, Gd) were prepared by solid state reaction method and characterized by powder X-ray diffraction. The room temperature elastic behavior of these materials was investigated by employing ultrasonic pulse transmission technique at 1 MHz. The values of elastic constants were computed from longitudinal and shear velocities. The measured values were corrected to zero porosity using Hasselman and Fulrath's formulae. The variation of elastic moduli with the size of rare earth ion is interpreted in terms of strength of interatomic bonding.
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 113-116
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
EPR characteristics of activated carbon for hydrogen production by the thermo-catalytic decomposition of methane
Autorzy:
Więckowski, A.
Najder-Kozdrowska, L.
Rechnia, P.
Malaika, A.
Krzyżyńska, B.
Kozłowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/1158900.pdf
Data publikacji:
2016-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.35.+r
61.66.Hq
76.30.-v
82.30.Lp
82.65.+r
88.30.ej
Opis:
The electron paramagnetic resonance (EPR) method was used to characterize samples of activated coal before and after reactions of the catalytic decomposition of methane and ethanol at temperatures of 1023 K (750°C), 1123 K (850°C) and 1223 K (950°C). The EPR parameters: spectroscopic splitting factor g, peak-to-peak linewidth ΔBₚₚ, and spin concentration c were measured. During the ethanol-assisted catalytic decomposition of methane carbon-located-spin radicals are partially transformed into oxygen-located-spin radicals.
Źródło:
Acta Physica Polonica A; 2016, 130, 3; 701-704
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Laguerre polynomial solutions of a class of initial and boundary value problems arising in science and engineering fields
Autorzy:
Gürbüz, B.
Sezer, M.
Powiązania:
https://bibliotekanauki.pl/articles/1061583.pdf
Data publikacji:
2016-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
02.30.Gp
02.30.Hq
02.70
Opis:
In this study, we consider high-order nonlinear ordinary differential equations with the initial and boundary conditions. These kinds of differential equations are essential tools for modelling problems in physics, biology, neurology, engineering, ecology, economy, astrophysics, physiology and so forth. Each of the mentioned problems are described by one of the following equations with the specific physical conditions: Riccati, Duffing, Emden-Fowler, Lane Emden type equations. We seek the approximate solution of these special differential equations by means of a operational matrix technique, called the Laguerre collocation method. The proposed method is based on the Laguerre series expansion and the collocation points. By using the method, the mentioned special differential equations together with conditions are transformed into a matrix form which corresponds to a system of nonlinear algebraic equations with unknown Laguerre coefficients, and thereby the problem is approximately solved in terms of Laguerre polynomials. In addition, some numerical examples are presented to demonstrate the efficiency of the proposed method and the obtained results are compared with the existing results in literature.
Źródło:
Acta Physica Polonica A; 2016, 130, 1; 194-197
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Solutions for conservative nonlinear oscillators using an approximate method based on Chebyshev series expansion of the restoring force
Autorzy:
Beléndez, A.
Hernández, A.
Beléndez, T.
Pascual, C.
Alvarez, M.
Arribas, E.
Powiązania:
https://bibliotekanauki.pl/articles/1075577.pdf
Data publikacji:
2016-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
02.30.Hq
02.30.Mv
05.45.-a
Opis:
Approximate solutions for small and large amplitude oscillations of conservative systems with odd nonlinearity are obtained using a "cubication" method. In this procedure, the Chebyshev polynomial expansion is used to replace the nonlinear function by a third-order polynomial equation. The original second-order differential equation, which governs the dynamics of the system, is replaced by the Duffing equation, whose exact frequency and solution are expressed in terms of the complete elliptic integral of the first kind and the Jacobi elliptic function cn, respectively. Then, the exact solution for the Duffing equation is the approximate solution for the original nonlinear differential equation. The coefficients for the linear and cubic terms of the approximate Duffing equation - obtained by "cubication" of the original second-order differential equation - depend on the initial oscillation amplitude. Six examples of different types of common conservative nonlinear oscillators are analysed to illustrate this scheme. The results obtained using the cubication method are compared with those obtained using other approximate methods such as the harmonic, linearized and rational balance methods as well as the homotopy perturbation method. Comparison of the approximate frequencies and solutions with the exact ones shows good agreement.
Źródło:
Acta Physica Polonica A; 2016, 130, 3; 667-678
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transmission matrix and Faraday rotation in a structure composed of over-dense magnetized plasma, dielectric, and prism layers
Autorzy:
Nejati, M.
Rajaei, L.
Powiązania:
https://bibliotekanauki.pl/articles/1058194.pdf
Data publikacji:
2016-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.25.Xz
52.59.Hq
Opis:
In this study, the anomalous transmission of wave through over-dense magnetized plasma is investigated. Electromagnetic waves propagate in over-dense matter through an excitation of the surface waves. For excitation of the surface waves, the structure of the prism, dielectric and magnetized over-dense plasma are considered. Variations in the transmitted and reflected amplitudes with the incident angle θ is investigated. Moreover, the effect of the thicknesses of the dielectric and plasma layers and that of the plasma and cyclotron frequencies on the transmitted wave amplitude are studied. In addition, the Faraday rotation of the transmitted and reflected waves as functions of the incident angle is investigated. The effect of various parameters on the Faraday rotation is considered. The prism currently deployed in this structure decreases the restriction of dielectric constant and provides conditions for actual construction.
Źródło:
Acta Physica Polonica A; 2016, 130, 6; 1346-1351
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Buckling Analysis of a Rotationally Restrained Single Walled Carbon Nanotube
Autorzy:
Yayli, M.
Powiązania:
https://bibliotekanauki.pl/articles/1398664.pdf
Data publikacji:
2015-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
03.65.Db
02.30.Nw
02.30.Hq
61.46.+w
Opis:
This paper presents an analytical formulation of nonlocal elasticity theory for the buckling analysis of simply supported carbon nanotubes with rotational springs at both ends. The lateral displacement function is represented by a Fourier sine series expansion. Stoke's transformation is applied to construct the coefficient matrix of the corresponding systems of linear equations. This matrix gives more flexibility in boundary conditions. The accuracy of proposed method is validated for three well-known boundary conditions available in the literature. A very good agreement has been obtained. The present method permits to have more efficient stability matrix for calculating the buckling loads of carbon nanotubes with any desired boundary conditions.
Źródło:
Acta Physica Polonica A; 2015, 127, 3; 678-683
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Groups of Paramagnetic Centres in Reduced and Methylated Low Rank Coal
Autorzy:
Pilawa, B.
Wachowska, H.
Kozłowski, M.
Więckowski, A.
Najder-Kozdrowska, L.
Powiązania:
https://bibliotekanauki.pl/articles/1401865.pdf
Data publikacji:
2015-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.35.+r
61.66.Hq
76.30.-v
76.30.Rn
89.30.ag
Opis:
Low rank Illinois No. 6 coal was studied by electron paramagnetic resonance EPR spectroscopy. The parameters of EPR spectra (spectroscopic splitting factors g, linewidths $\DeltaB_{pp}$, concentrations of paramagnetic centres N) were measured for row and chemically treated coal (demineralized, reduced and methylated samples). The multi-component structure of experimental spectra of this coal was proved. Two groups of paramagnetic centres responsible for broad Lorentzian 1 and narrow Lorentzian 2 lines exist in studied samples. Paramagnetic centres connected with component lines revealed different behaviour during chemical treatments.
Źródło:
Acta Physica Polonica A; 2015, 128, 3; 264-267
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation of Radiation Effects in SiO₂/Si Structures
Autorzy:
Komarov, F.
Zayats, G.
Komarov, A.
Miskiewicz, S.
Michailov, V.
Komsta, H.
Powiązania:
https://bibliotekanauki.pl/articles/1402212.pdf
Data publikacji:
2015-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
02.30.Hq
02.60.Cb
Opis:
The space-time evolution of electric charge induced in the dielectric layer of simulated metal-insulator-semiconductor structures due to irradiation with X-rays is discussed. The system of equations used as a basis for the simulation model is solved iteratively by the efficient numerical method. The obtained simulation results correlate well with the respective data presented in other scientific publications.
Źródło:
Acta Physica Polonica A; 2015, 128, 5; 857-860
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Explicit Analytic Solution to the Thomas-Fermi Equation by the Improved Differential Transform Method
Autorzy:
Fatoorehchi, H.
Abolghasemi, H.
Powiązania:
https://bibliotekanauki.pl/articles/1198516.pdf
Data publikacji:
2014-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
02.30.Hq
02.30.Mv
02.60.Lj
21.10.Ft
31.15.-p
Opis:
In this paper, a newly proposed analytical scheme by the authors namely the improved differential transform method is employed to provide an explicit series solution to the Thomas-Fermi equation. The solution procedure is very straightforward, requiring merely elementary operations together with differentiation, and ends up in a recursive formula involving the Adomian polynomials to afford the unknown coefficients. Unlike many other methods, our approach is free of integration and hence can be of computational interest. In addition, a very good agreement between the proposed solution and the results from several well-known works in the literature is demonstrated.
Źródło:
Acta Physica Polonica A; 2014, 125, 5; 1083-1087
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 55

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