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    Tytuł:
    Gradient copolymers from aromatic and aliphatic 2-oxazolines as promising biomedical materials
    Autorzy:
    Kronek, J.
    Petrenćíková, N.
    Kroneková, Z.
    Datta, S.
    Jancura, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/284876.pdf
    Data publikacji:
    2018
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
    Tematy:
    copolymers
    biomaterials
    gradient
    Źródło:
    Engineering of Biomaterials; 2018, 21, 148; 96
    1429-7248
    Pojawia się w:
    Engineering of Biomaterials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    New estimate for the curvature of an order-convex set and related questions
    Autorzy:
    Ramazanov, Ali B.
    Powiązania:
    https://bibliotekanauki.pl/articles/2050043.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Instytut Badań Systemowych PAN
    Tematy:
    gradient
    estimates
    curvature
    convexity
    algorithm
    Opis:
    It is well known that in discrete optimization problems, gradient (local) algorithms do not always guarantee an optimal solution. Therefore, the problem arises of finding the accuracy of the gradient algorithm. This is a fairly well-known problem and numerous publications have been devoted to it. In establishing accuracy, various approaches are used. One of these approaches is to obtain guaranteed estimates of the accuracy of the gradient algorithm in terms of the curvature of the admissible domain. With this approach, it is required to find the curvatures of the admissible region. Since finding the exact value of curvature is a difficult problem to solve, curvature estimates in terms of more or less simply calculated parameters of the problem are relevant. A new improved bound for the curvature of an order-convex set is found and is presented in this paper in terms of the steepness and parameters of strict convexity of the function.
    Źródło:
    Control and Cybernetics; 2020, 49, 2; 233-240
    0324-8569
    Pojawia się w:
    Control and Cybernetics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analiza wytrzymałościowa i odkształceniowa biomateriałów gradientowych przeznaczonych na implanty
    Strength and strain analysis of gradient biomaterials assigned for medical implants
    Autorzy:
    Migacz, K.
    Chłopek, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/285478.pdf
    Data publikacji:
    2009
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
    Tematy:
    implanty
    biomateriały
    gradient
    implants
    biomaterials
    Opis:
    W pracy autorzy przedstawiają analizę wytrzymałościową i odkształceniową kompozytów gradientowych z kontrolowaną zmianą modułu Younga w warunkach symulowanego środowiska biologicznego. Zaprojektowane przy pomocy MES pięciowarstwowe kompozyty z PSU/CF 1D z gradientem otrzymanym poprzez zmianę udziału procentowego włókien (10, 15, 20, 30, 40%) po wstępnych testach wytrzymałościowych i odkształceniowych zostały umieszczone w płynie Ringera pod działaniem stałego obciążenia siłą P=1200N przez okres 56 dni. Co 14 dni wykonywano pomiary ultradźwiękowe, po okresie inkubacji próbki poddano badaniom wytrzymałościowym do 5000 N. Wyniki pomiarów wykazują przydatność materiału gradientowego PSU/CF 1D jako implantów dokręgosłupowych ze względu na ich dobrze dopasowany moduł Younga i odkształcalność do naturalnego krążka międzykręgowego człowieka. W kolejnym etapie badań zostanie wykonana analiza zmęczeniowa materiałów w celu określenia ich trwałości.
    In this article strength and strain analysis of gradient composites with controlled change of Young’s modulus in simulated biological environment was presented. Polysulfon/carbon fibers (PSU/CF) 1D composites with gradient of the content of PSU to CF (10, 15, 20, 30, 40 wt% of CF), built up of 5 layers were designed by using FEM. After preliminary strength and strain tests they were incubated in Ringer’s under the static load P=1200 N solution for 56 days. Ultrasonic measurements were made every 14 days. After incubation samples mechanical strength was tested with the load up to 5000 N. The obtained results show suitability of PSU/CF 1D gradient material for spine implants because of well – matched Young’s modulus and deformability to natural human intervertebral disc. As a next step of the research fatigue testing analysis will be done, in order to obtain materials’ durability.
    Źródło:
    Engineering of Biomaterials; 2009, 12, no. 89-91; 176-179
    1429-7248
    Pojawia się w:
    Engineering of Biomaterials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mechanical properties of a-C:H/Ti layers on prosthodontic CoCr and NiCr alloys
    Autorzy:
    Szymański, W.
    Batory, D.
    Cłapa, M.
    Klimek, L.
    Powiązania:
    https://bibliotekanauki.pl/articles/284500.pdf
    Data publikacji:
    2009
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Polskie Towarzystwo Biominerałów
    Tematy:
    carbon layer
    corrosion
    wear resistance
    dental implant
    gradient
    methalosis
    Opis:
    Co-Cr and Ni-Cr alloys are widely used in dental implants production. However, there is a risk connected with application of this kind of materials like allergy and methalosis caused by Cr, Ni ions, very dangerous for patients’ health and life. Moreover metal ions released into human body can affect inflammation of the surrounding tissue. Biomaterials’ surface treatment by the deposition of diamond-like carbon films can noticeably improve the corrosion and mechanical features. Widely discussed in world’s literature problems with adhesion of DLC layers can be solved by the deposition of gradient a-C:H/Ti layer. Due to that, it is possible to manufacture thick and well adherent carbon layer on the implant’s surface which will constitute a very good protection against wear and corrosion. Our goal was to evaluate the mechanical properties of a-C:H/Ti layers deposited on CoCr and NiCr alloys in hybrid deposition system RF PACVD/MSand to find the influence of layer thickness on the selected properties. As the result of the investigation it was noticed that deposition of a-C:H/Ti layer improves the mechanical properties of CoCr and NiCr alloys. High hardness and good adhesion of gradient carbon layers makes them a very perspective material for this kind of applications.
    Źródło:
    Engineering of Biomaterials; 2009, 12, 85; 2-5
    1429-7248
    Pojawia się w:
    Engineering of Biomaterials
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    On the blowing up solutions of the 4-d general q-Kuramoto-Sivashinsky equation with exponentially “dominated” nonlinearity and singular weight
    Autorzy:
    Baraket, Sami
    Mahdaoui, Safia
    Ouni, Taieb
    Powiązania:
    https://bibliotekanauki.pl/articles/29519212.pdf
    Data publikacji:
    2023
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    singular limits
    Green’s function
    nonlinearity
    gradient
    nonlinear domain decomposition method
    Opis:
    Let Ω be a bounded domain in $ \mathbb{R}^4 $ with smooth boundary and let $ x^1, x^2, . . . , x^m $ be m-points in Ω. We are concerned with the problem $ \Delta^2 u - H(x, u, D^k u)=\rho^4 \prod_{i=1}^n | x - p_i |^{4 \alpha_i } f(x)g(u), $ where the principal term is the bi-Laplacian operator, $ H(x, u, D^k u)$ is a functional which grows with respect to $ Du $ at most like $ |Du|^q, 1 ≤ q ≤ 4, f : Ω → [0,+∞[ $ is a smooth function satisfying f(pi) > 0 for any i = 1, . . . , n, $ α_i $ are positives numbers and $ g : \mathbb{R} → [0,+∞[ $ satisfy $ |g(u)| ≤ ce^u $. In this paper, we give sufficient conditions for existence of a family of positive weak solutions $ (u_ρ)_{ρ>0} $ in Ω under Navier boundary conditions u = Δu = 0 on ∂Ω. The solutions we constructed are singular as the parameters ρ tends to 0, when the set of concentration $ S = {x^1, . . . , x^m} ⊂ Ω $ and the set $ Λ := {p_1, . . . , p_n} ⊂ Ω $ are not necessarily disjoint. The proof is mainly based on nonlinear domain decomposition method.
    Źródło:
    Opuscula Mathematica; 2023, 43, 1; 5-18
    1232-9274
    2300-6919
    Pojawia się w:
    Opuscula Mathematica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A Hydrophysical Analysis of Urban Surface Runoff, Channel Characteristics, and the Incidence of Flood and Erosion Over the Calabar Drainage Area, Nigeria
    Autorzy:
    Ugbong, I. A.
    Budagov, I. V.
    Powiązania:
    https://bibliotekanauki.pl/articles/952348.pdf
    Data publikacji:
    2016
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    drainage
    channels
    runoff volume
    flood and erosion
    gradient
    drainage area
    channel length
    Opis:
    Hydro-physical processes operating in the Calabar drainage area were analyzed by estimating the volume of surface runoff carried in each basin and sub-basin, using field measurements of flow velocities in conjunction with the “Rational Method” mathematical model proposed by civil and environmental engineers. It was found that run-off flow is affected by at least three factors which either produce floods or erosion conditions. The factors include size of catchment areas, gradient and lengths of flow channels. The Multiple Regression statistic was used to test these relationships. The results showed a strong statistical correlation among these variables, as well as between these variables and flow characteristics. It was found that for all the basins, runoff volume increased with increasing surface area of the catchment; just as areas with lower elevations register higher flow volume accompanied by flooding; with a reversed condition in higher ground where higher velocities are found with resultant erosion conditions. Also channels with considerable lengths receive higher flows along their courses downstream, and thus produce floods. It was therefore, recommended that in addition to the six major drainage channels recommended for the area, each channel and each segment of a channel should be determined by its gradient, drainage area, length of flow channel.
    Źródło:
    Journal of Ecological Engineering; 2016, 17, 3; 30-40
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    The gradient and the divergence for vector-valued forms
    Autorzy:
    Klekot, Agnieszka
    Pierzchalski, Antoni
    Powiązania:
    https://bibliotekanauki.pl/articles/2202058.pdf
    Data publikacji:
    2023
    Wydawca:
    Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
    Tematy:
    vector forms
    gradient
    divergence
    Laplacians on vector forms
    Weitzenbock type formula
    postać wektorowa
    dywergencja
    Opis:
    On a Riemannian manifold, two differential operators: the gradient and the divergence are defined and investigated in the bundle of alternating differential forms of any degree with values in a vector bundle. Several algebraic, analytic and geometric properties of the two operators are derived. The vector character of the gradient on forms turns out to be a source of possible applications.
    Źródło:
    Journal of Applied Mathematics and Computational Mechanics; 2023, 22, 1; 31--45
    2299-9965
    Pojawia się w:
    Journal of Applied Mathematics and Computational Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Wpływ czynników geograficznych na klimat Europy
    The impact of geographical factors on the climate in Europe
    Autorzy:
    Stopa-Boryczka, M.
    Boryczka, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/2084803.pdf
    Data publikacji:
    2009
    Wydawca:
    Uniwersytet Warszawski. Wydział Geografii i Studiów Regionalnych
    Tematy:
    Europa
    czynniki geograficzne
    klimat
    gradient
    temperatura powietrza
    naslonecznienie
    opady
    cisnienie atmosferyczne
    predkosc wiatru
    wiatry
    Opis:
    The main purpose of the study was to define the most important features of the climate of Europe, which derive from geographical position and altitude above sea level. To begin with, we discuss the thermal features of Europe's climate which result from the continent's location at moderate latitudes. The research was conducted on the basis of average monthly values of air temperature in 30-year periods, 1961-1990. The fields of real sunshine, air temperature, atmospheric precipitation, atmospheric pressure and wind velocity were described using empirical models - regression polynomials of the second degrees y = f (φ), y= f (λ), y = f (H) for three coordinates: latitude φ, longitude λ and altitude above sea level H. They simulate both the zonal variability of air temperature T(φ) and precipitations P(φ) (which depends on the incoming solar radiation) and the impact of the Atlantic Ocean and the altitude T(λ), P(λ). The equation of the regression hyperplane has been a good tool for the inverstigation of general features of Europe's climate: y = a₀ +a₁ φ+a₂ λ + a₃ H. Coefficients of partia! a₁, a₂, a₃ - are components of gradients of meteorological variables; a₁ - meridional gradient, in °C/1° φ; a₂ - latitudinal gradient, in °C/1 °λ; a₃ - hypsometric gradient, in °C/100 m.
    Źródło:
    Prace i Studia Geograficzne; 2009, 41; 191-208
    0208-4589
    Pojawia się w:
    Prace i Studia Geograficzne
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Some differential operators in the symmetric bundle
    Autorzy:
    Kimaczyńska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/122502.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
    Tematy:
    symmetric tensors
    symmetric derivative
    gradient
    divergence
    Weitzenböck type formula
    operator różnicowy
    tensory symetryczne
    pochodna symetryczna
    Opis:
    Some natural differential operators in the bundles of symmetric tensors and symmetric tensors with values in the tangent bundle are investigated. Applications in geometry, physics and tomography are also reviewed.
    Źródło:
    Journal of Applied Mathematics and Computational Mechanics; 2017, 16, 3; 27-36
    2299-9965
    Pojawia się w:
    Journal of Applied Mathematics and Computational Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Distribution patterns of three Potamogeton species (P. crispus, P. nodosus and P. pectinatus) along velocity and base richness gradients from a lowland river
    Autorzy:
    Jakubas, E.
    Gabka, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/878331.pdf
    Data publikacji:
    2013
    Wydawca:
    Uniwersytet Przyrodniczy w Poznaniu
    Tematy:
    distribution pattern
    Potamogeton
    Potamogeton crispus
    Potamogeton nodosus
    Potamogeton pectinatus
    abundance
    hydrophyte
    gradient
    lowland river
    river
    environment
    Natura 2000 area
    Opis:
    This study presents distribution and abundance of three Potamogeton species, namely Potamogeton crispus, P. nodosus and P. pectinatus along environmental gradients in the lowland river Wełna (NW Poland). The relationships between 13 environmental factors and the pattern aquatic vegetation distribution along river were investigated. Among ecological factors rarely undertaken in aquatic ecology the light climate was concerned. It is postulated that the Potamogeton communities in the investigated river are strongly connected with water velocity, substrate of bottom and light conditions, in particular dissolved organic matter (DOM). Elodeo-Potametum crispi and algae communities with dominant species Hildenbrandia rivularis were well developed in the places shading by trees, with high velocity and fairly clean water, mostly with stony bottom. Potametum nodosi was noted in mean values of velocity and medium water quality with high content of organic matter in the bottom substrate. The last investigated community Sparganio-Potametum interrupti was found in poor water quality with the highest values of electric conductivity. The obtained results give a new approach of the ecology and abiotic typology of rivers with macrophytes including abundance of Potamogeton species (Nature 2000 habitat, code 3260 – “Water courses of plain to montane levels with the Ranunculion fl uitantis and Callitricho-Batrachion vegetation”).
    Źródło:
    Roczniki Akademii Rolniczej w Poznaniu. Botanika-Steciana; 2013, 17
    1896-1908
    Pojawia się w:
    Roczniki Akademii Rolniczej w Poznaniu. Botanika-Steciana
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-10 z 10

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