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Wyświetlanie 1-15 z 1552
Tytuł:
Flow coefficient of the aggregates as a parameter characterizing the suitability of non-cohesive soils for earthworks
Autorzy:
Majer, Stanisław
Powiązania:
https://bibliotekanauki.pl/articles/118735.pdf
Data publikacji:
2020
Wydawca:
Szkoła Główna Gospodarstwa Wiejskiego w Warszawie. Wydawnictwo Szkoły Głównej Gospodarstwa Wiejskiego w Warszawie
Tematy:
flow coefficient of aggregates
uniformity coefficient
Opis:
The article presents the results of the flow coefficient of aggregate for 30 sands and aggregates. The introduction of European standards for the assessment of construction aggregates over 20 years ago introduced a number of new testing methods not previously used in Poland. One of them is the flow coefficient of aggregate, popularly called aggregate angularity. The method of determination is given in the standard PN-EN 933-6:2014. This standard defines the method of determining the index for coarse aggregates with grain sizes between 4 and 20 mm and fine aggregates with grain sizes below 2 mm. This test is particularly important when designing mineral-asphalt mixtures. Aggregate angularity, particularly in fine aggregates, is the main factor influencing the workability of mixtures. The flow time through the apparatus depends on the degree of roundness and form of the grain. The study determined the relationship between the flow coefficient of aggregate and CBR in relation to the uniformity coefficient. This indicator is still considered to be one of the main parameters that affect the suitability of non-cohesive soils in earthworks. It was proven that Ecs is more dependent on CBR than CU.
Źródło:
Scientific Review Engineering and Environmental Sciences; 2020, 29, 3; 298-307
1732-9353
Pojawia się w:
Scientific Review Engineering and Environmental Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Liquid Forging Pressure on Solubility and Freezing Coefficients of Cast Aluminum 2124, 2218 and 6063 Alloys
Autorzy:
Tirth, Vineet
Arabi, Amir
Powiązania:
https://bibliotekanauki.pl/articles/354280.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
liquid forging
porosity
hardness
solubility coefficient
freezing coefficient
Opis:
Liquid forging alias squeeze casting gives the combined advantage of casting and forging. Optimum process parameters are important to get a cost-efficient process. In this study, four materials have been identified, which are extensively used in industries. These materials are commercially pure Al and three Al-alloys namely, 2124, 2218 and 6063. The pouring temperature and the mold temperature is maintained at 700°C and 250°C respectively. The materials were developed at seven pressure variations from 0 to 150 MPa. The effect of the pressure on the microstructures, porosity, and hardness has been reported. The coefficient of solubility is estimated for all materials and a polynomial relationship is found to be the best fit with the applied pressure. The pressure of 100 MPa gives better increment in hardness. The melting point and the freezing coefficient of the materials under study have been determined. A linear relationship between the pressure and the freezing time is deduced. It is observed that the solubility and the freezing coefficients depend on the pressure as well, in addition to the composition and temperature.
Źródło:
Archives of Metallurgy and Materials; 2020, 65, 1; 357-366
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reactive solute transport in blood flow through a permeable capillary
Autorzy:
Debnath, S.
Roy, A. K.
Bég, O. A.
Powiązania:
https://bibliotekanauki.pl/articles/38695392.pdf
Data publikacji:
2022
Wydawca:
Instytut Podstawowych Problemów Techniki PAN
Tematy:
capillary
axial flow
radial flow
solute dispersion
Gill decomposition
filtration coefficient
exchange coefficient
advection coefficient
Opis:
The present analysis discusses the solute transport process in a steady 2D (axial and radial) laminar flow of blood through a permeable, finite length capillary. Blood is treated as a homogeneous Newtonian fluid and the solute is absorbed at the capillary wall with a linear irreversible reaction rate. The velocity profile is obtained by a regular perturbation technique, whereas the transport coefficients depicted by the Gill generalized dispersion model are solved numerically. A number of different scenarios are considered, namely transport with no-reaction, weak absorption, strong absorption, low filtration or high filtration, etc. In the initial stages, the temporal behaviour of the dispersion coefficient is identical to those cases when there is no radial velocity. For the combined effect of radial and axial velocities, however, the dispersion coefficient is lower for a high absorption rate than for a weak absorption rate. Diffusion is accelerated with higher values of filtration coefficient. Owing to the opposite effects of radial diffusion and radial velocity, the solute particles require more time to reach the steady state. The analysis finds applications in, for example, reactive nutrient and pharmacological transport in capillary hemodynamics.
Źródło:
Archives of Mechanics; 2022, 74, 2-3; 173-200
0373-2029
Pojawia się w:
Archives of Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heave motion of a vertical cylinder with heave plates
Autorzy:
Ciba, Ewelina
Powiązania:
https://bibliotekanauki.pl/articles/1573695.pdf
Data publikacji:
2021
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
spar platforms
heave plates
damping coefficient
added mass coefficient
Opis:
The shape of a vertical cylinder resembles the classic form of a spar platform. Spar platforms are floating platforms that are successfully used in waters of great depths and have several advantages that mean they are readily used in the oil industry. Many of these advantages are also relevant to their application for offshore wind turbines, which is currently being considered. In the hydrodynamic analysis of spar platforms, the determination of their hydrodynamic coefficients plays an important role. They can be determined based on the free decay test. The study presents a method for determining the hydrodynamic coefficients of an object based on the free decay test. The results of free oscillation calculations with the help of numerical fluid mechanics tools are presented and compared with the results of the experiment and analytical solution. The application of determined coefficients and their significance for floating platforms are discussed. The influence of change in the form of an additional damping element on the behaviour of spar structures is shown.
Źródło:
Polish Maritime Research; 2021, 1; 42-47
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of the Presence of Vegetations in Floodplains on Flood Risks
Autorzy:
Walczak, N.
Hammerling, M.
Spychała, M.
Nieć, J.
Powiązania:
https://bibliotekanauki.pl/articles/123654.pdf
Data publikacji:
2015
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
flood area
flow velocity
resistance coefficient
roughness coefficient
vegetation
Opis:
The movement of water on flood areas depends mainly on the geometric parameters of vegetation, which as a dynamic factor causes a high changeability of flow conditions during the year. The actual ecological trend, whereby there is a tendency to leave the plants in the floodplain, imposes the necessity on engineers to develop accurate methods of determining the effect of vegetation on what used to be once a commonly occurring flood risk. According to the report on national security risk, elaborated by the Government Security Centre, flooding is the most common such risk. This is most likely to occur among all the risks included in the National Crisis Management Plan and brings the greatest number of negative effects. In order to mitigate the negative phenomena related to floodplains, the methodology and calculation of the average flows, using the Maninng and Darcy-Weisbach models is presented.
Źródło:
Journal of Ecological Engineering; 2015, 16, 5; 160-167
2299-8993
Pojawia się w:
Journal of Ecological Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Method of Removal Yttrium (III) and Ytterbium (III) From Dilute Aqueous Solutions
Autorzy:
Lobacheva, O.
Dzhevaga, N.
Danilov, A.
Powiązania:
https://bibliotekanauki.pl/articles/123428.pdf
Data publikacji:
2016
Wydawca:
Polskie Towarzystwo Inżynierii Ekologicznej
Tematy:
ion flotation
sodium dodecyl sulfate
distribution coefficient
separation coefficient
removal
Opis:
Yttrium (III) and ytterbium (III) cations ion flotation from diluted aqueous solutions in the presence of chloride ions using sodium dodecyl sulfate as collector agent were studied. Y (III) and Yb (III) distribution and recovery coefficients as a function of aqueous phase рН value at different sodium chloride concentrations were received. Yttrium (III) and ytterbium (III) chloro and hydroxo complexes instability constants were calculated. The calculation of separation coefficient at рН specified values depending on chloride ion concentration was conducted. Maximum separation coefficient was observed when chloride concentration of 0.01 M is 50 at рН 7.8. Ksep is minimal in nitrate medium ans is 3 at рН 7.0. At sodium chloride concentration of 0.05 М Ksep is 9 at рН 7.8.
Źródło:
Journal of Ecological Engineering; 2016, 17, 2; 38-42
2299-8993
Pojawia się w:
Journal of Ecological Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impact of friction coefficient on particles circulation velocity calculated by euler-lagrange model in spouted bed apparatus for dry coating
Autorzy:
Ludwig, W.
Powiązania:
https://bibliotekanauki.pl/articles/297983.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Warmińsko-Mazurski w Olsztynie
Tematy:
spout-fluid bed
friction coefficient
restitution coefficient
Euler-Lagrange approach
Opis:
This paper is a continuation of research concerning gas-solid flow modelling using the Euler-Lagrange approach in a spout-fluid bed apparatus. The major challenge in this case was to determine the friction coefficient for particles hitting against the walls of the apparatus. On the basis of the properties of similar materials the value of this quantity was estimated at 0.2. Therefore, it proved useful to check the model’s sensitivity to the value of this parameter. The study investigated the effect of friction coefficient on calculated values of particles velocity in the draft tube and the annular zone of the device for various volumes of the circulating bed. In the course of calculations, a relatively small influence of friction coefficient on particles velocity was observed in the tested zones of the apparatus. The changes were most visible for large volumes of the bed, which was connected with an increase in the number of collisions of particles with the walls.
Źródło:
Technical Sciences / University of Warmia and Mazury in Olsztyn; 2018, 21(4); 303-321
1505-4675
2083-4527
Pojawia się w:
Technical Sciences / University of Warmia and Mazury in Olsztyn
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Virtual synchronous generator frequency response study of energy computing and storage devices
Autorzy:
Zhang, Baoge
Ping, Shanyan
Long, Yi
Jiao, Yuemin
Wu, Boxiang
Powiązania:
https://bibliotekanauki.pl/articles/2172798.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
damping coefficient
energy storage capacit
inertia coefficient
virtual synchronous machine
Opis:
Renewable energy sources are connected to the grid through inverters, resulting in reduced grid inertia and poor stability. Traditional grid-connected inverters do not have the function of voltage and frequency regulation and can no longer adapt to the new development. The virtual synchronous generator (VSG) has the function of voltage and frequency regulation and has more outstanding advantages than the traditional inverter. Based on the principle of the VSG, the relationship between energy storage capacity, frequency response and output power of the VSG is derived, and the relationship between the virtual inertia coefficient, damping coefficient and frequency characteristics of the VSG and output power is revealed. The mathematical model is established and modeled using the Matlab/Simulink simulation software, and the simulation results verify the relationship between energy storage capacity and frequency response and the output power of the VSG.
Źródło:
Archives of Electrical Engineering; 2022, 71, 4; 895--907
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Asymmetrical PZT Applied to Active Reduction of Asymmetrically Vibrating Beam – Semi-Analytical Solution
Autorzy:
Brański, Adam
Kuras, Romuald
Powiązania:
https://bibliotekanauki.pl/articles/31339957.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
beam
actuator (PZT)
active vibration reduction
vibration reduction coefficient
effectiveness coefficient.
Opis:
The article extended the idea of active vibration reduction of beams with symmetric modes to beams with asymmetric modes. In the case of symmetric modes, the symmetric PZT (s-PZT) was used, and the optimization of the problem led to the location of the s-PZT centre at the point with the greatest beam curvature. In the latter case, the asymmetric modes that occur due to the addition of the point mass cause an asymmetric distribution of the bending moment and transversal displacement of a beam. In this case, the optimal approach to the active vibration reduction requires both new asymmetric PZT (a-PZT) and its new particular distribution on the beam. It has been mathematically determined that the a-PZT asymmetry point (a-point), ought to be placed at the point of maximum beam bending moment. The a-PZT asymmetry was found mathematically by minimizing the amplitude of the vibrations. As a result, it was possible to formulate the criterion of the maximum bending moment of the beam. The numerical calculations confirmed theoretical considerations. So, it was shown that in the case of asymmetric vibrations, the a-PZTs reduced vibrations more efficiently than the s-PZT.
Źródło:
Archives of Acoustics; 2022, 47, 4; 555-564
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
New paradigms of quantification of economic efficiency in the transport sector
Autorzy:
Poliak, Milos
Svabova, Lucia
Konecny, Vladimir
Zhuravleva, Natalia Aleksandrovna
Culik, Kristian
Powiązania:
https://bibliotekanauki.pl/articles/19233644.pdf
Data publikacji:
2021
Wydawca:
Instytut Badań Gospodarczych
Tematy:
transport
coefficient
calculation
cost
Opis:
Research background: In determining the prices in road transport, carriers usually use the calculations based on a so-called routes utilisation coefficient, which allows the carrier to also take the possibility of the return rides without load into account. Currently, it is usually used as a constant from the interval from zero to one. Purpose of the article: Considering a different offer of return transport from individual European Union (EU) countries, it can be assumed that the routes utilisation coefficient should have different values because there is a varying level of non-zero probability that the vehicle will return without a load. This study therefore proposes a new approach to determining the value of this coefficient based on transport direction. The study also aims to identify clusters of EU countries, for which the common value of the coefficient should be set. Methods: The Analysis of Variance (ANOVA) test was used to verify the assumption of the differences among the means of transport offers. Cluster analysis was used to identify the aforementioned groups of countries. This analysis is based on real data on transport offers to Slovakia from 18 different EU countries. Findings & value added: The results of the analysis can also be used in other EU countries because if significant differences in transport offers to Slovakia exist in individual countries, there is a reasonable assumption that this conclusion will also be valid in other countries. The analysis demonstrated that it is more appropriate to use the routes utilisation coefficient with various values, dependent on the transport direction. For the transport companies, implementation of the obtained results into practice is beneficial to increase their competitiveness through the more precise setting of transport prices, but also to the optimisation of the transport price itself with regard to the expected costs.
Źródło:
Oeconomia Copernicana; 2021, 12, 1; 193-212
2083-1277
Pojawia się w:
Oeconomia Copernicana
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On coefficient inequalities in the Carathéodory class of functions
Autorzy:
Lecko, Adam
Powiązania:
https://bibliotekanauki.pl/articles/1207925.pdf
Data publikacji:
2000
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
Carathéodory class
coefficient inequalities
Opis:
Some inequalities are proved for coefficients of functions in the class P(α), where α ∈ [0,1), of functions with real part greater than α. In particular, new inequalities for coefficients in the Carathéodory class P(0) are given.
Źródło:
Annales Polonici Mathematici; 2000, 75, 1; 59-67
0066-2216
Pojawia się w:
Annales Polonici Mathematici
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of roughness coefficient of the underside of ice cover
Autorzy:
Majewski, W.
Powiązania:
https://bibliotekanauki.pl/articles/241490.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
Tematy:
ice cover
roughness coefficient
Opis:
The formation of ice cover in winter on rivers, channels and run-of-reservoirs, changes flow characteristics significantly. Calculations of water surface profiles or discharge along a river reach with ice cover by means of 1-D models, requires detailed values of the roughness coefficients of the river bed and underside of the ice cover. Numerous studies dealing with roughness coefficients of the river bed with free surface flow were carried out in the past, however, very few investigations were performed on the determination of the roughness coefficient of the underside of ice cover. Data of calculations indicate that this coefficient may vary considerably with space and time, depending on the character of the ice cover, flow characteristics and meteorological conditions. In 1-D models roughness coefficient of the bed and of the underside of the ice cover must be combined into one composite roughness coefficient. The paper presents determination of roughness coefficient of the underside of ice cover based on velocity distributions in the Vistula River cross-sections with ice cover. It may be assumed that vertical velocity distribution has a logarithmic character in the regions near the bottom and ice cover. Taking into account this assumption the procedure for the calculation of Darcy-Weisbach friction factor f and Manning roughness coefficient n is proposed, basing on the data of velocity measurements in a given vertical. It was found that roughness coefficient of the underside of the ice cover varies in a much larger range than the bottom roughness coefficient and depends very much on the character of the ice cover.
Źródło:
Archives of Hydro-Engineering and Environmental Mechanics; 2003, 50, 3; 219-228
1231-3726
Pojawia się w:
Archives of Hydro-Engineering and Environmental Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sharing the Growth Dividend: Analysis of Inequality in Asia
Autorzy:
Jain-Chandra, Sonali
Kinda, Tidiane
Kochhar, Kalpana
Piao, Shi
Schauer, Johanna
Powiązania:
https://bibliotekanauki.pl/articles/2042921.pdf
Data publikacji:
2019-09-04
Wydawca:
Uniwersytet Warszawski. Wydawnictwo Naukowe Wydziału Zarządzania
Tematy:
Inequality
Gini coefficient
Asia
Opis:
This paper focusses on income inequality in Asia, its drivers and policies to combat it. It finds that income inequality has risen in most of Asia, in contrast to many other regions. While in the past, rapid growth in Asia has come with equitable distribution of the gains, more recently fastgrowing Asian economies have been unable to replicate the “growth with equity” miracle. There is a growing consensus that high levels of inequality can hamper the pace and sustainability of growth. The paper argues that policies could have a substantial effect on reversing the trend of rising inequality. It is imperative to address inequality of opportunities, in particular to broaden access to education, health, and financial services. Also, fiscal policy could combat rising inequality, including by expanding and broadening the coverage of social spending, improving tax progressivity, and boosting compliance. Further efforts to promote financial inclusion, while maintaining financial stability, can help.
Źródło:
Journal of Banking and Financial Economics; 2019, 2(12); 5-28
2353-6845
Pojawia się w:
Journal of Banking and Financial Economics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phenomenon of force impulse restitution in collision modelling
Zjawisko restytucji impulsów sił chwilowych w modelowaniu zderzeń
Autorzy:
Michalczyk, J.
Powiązania:
https://bibliotekanauki.pl/articles/280769.pdf
Data publikacji:
2008
Wydawca:
Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
Tematy:
collision
coefficient of restitution
Opis:
The rightness of the Newtonian hypothesis concerning a constat value of the coefficient of restitution R has been confirmed in the paper with reference to collisions in which the loss of energy occurs in conseqence of material damping. For collisions of different nature, when R depends on the density of the energy flux _, the paper points to the possibility of extending this notion to the case of eccentric collision. The possibility of describing R as a random function of _ has been shown as well.
W pracy wykazano, że Newtonowska idea wspłółczynnika restytucji R = const jest słuszna w odniesieniu do zderzeń, w których strata energii powstaje głównie na skutek tłumienia materiałowego. Dla zderzeń o innym charakterze, dla których R zależy od gęstości strumienia energii _, wskazano na możliwość rozszerzenia tego pojęcia na przypadek zderzenia mimośrodowego. W pracy wskazano również na celowość opisania R jako funkcji losowej parametru _ i podano formułę na siłę kontaktową zapewniającą uzyskanie założonej wartości R podczas symulacji cyfrowej procesu zderzenia.
Źródło:
Journal of Theoretical and Applied Mechanics; 2008, 46, 4; 897-908
1429-2955
Pojawia się w:
Journal of Theoretical and Applied Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Uniformly convex functions II
Autorzy:
Ma, Wancang
Minda, David
Powiązania:
https://bibliotekanauki.pl/articles/1311788.pdf
Data publikacji:
1993
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
convex functions
coefficient bounds
Opis:
Recently, A. W. Goodman introduced the class UCV of normalized uniformly convex functions. We present some sharp coefficient bounds for functions f(z) = z + a₂z² + a₃z³ + ... ∈ UCV and their inverses $f^{-1}(w) = w + d₂w² + d₃w³ + ...$. The series expansion for $f^{-1}(w)$ converges when $|w| < ϱ_f$, where $0 < ϱ_f$ depends on f. The sharp bounds on $|a_n|$ and all extremal functions were known for n = 2 and 3; the extremal functions consist of a certain function k ∈ UCV and its rotations. We obtain the sharp bounds on $|a_n|$ and all extremal functions for n = 4, 5, and 6. The same function k and its rotations remain the only extremals. It is known that k and its rotations cannot provide the sharp bound on $|a_n|$ for n sufficiently large. We also find the sharp estimate on the functional |μa²₂ - a₃| for -∞ < μ < ∞. We give sharp bounds on $|d_n|$ for n = 2, 3 and 4. For $n = 2, k^{-1}$ and its rotations are the only extremals. There are different extremal functions for both n = 3 and n = 4. Finally, we show that k and its rotations provide the sharp upper bound on |f''(z)| over the class UCV.
Źródło:
Annales Polonici Mathematici; 1993, 58, 3; 275-285
0066-2216
Pojawia się w:
Annales Polonici Mathematici
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 1552

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