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Wyświetlanie 1-15 z 20
Tytuł:
Stability of Micropolar Fluid in a Porous Medium Provoked by Heat Function and Radiation
Autorzy:
Nwabuzor, P. O.
Ngiangia, A. T.
Chukwuocha, E. O.
Powiązania:
https://bibliotekanauki.pl/articles/1076558.pdf
Data publikacji:
2019
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Electroconductivity
Heat Function
Micropolar Fluid
Rayleigh
Stability
Wave Number
Opis:
The stability of micropolar fluid flow in a channel under the influence of heat function, magnetic field and radiation was investigated. Using the similarity solution and non-dimensionalizing, the governing partial differential equations (PDEs) where transformed to a set of non-linear differential equations (ODEs). We therefore perturbed the system and determined the stability of the system. Wolfram 9 software (Mathematica) was used to analyze the various stability effect of the material parameters on the fluid flow. The graphical results reflects the expected physical behavior of the flow configuration under consideration. The study reveals that the Prandtl (Pr), wave (a), Radiation (R) and heat function parameters at a certain critical value of the wave number hastens the onset of stability. While the Electroconductivity (σ), Magnetic field (M), Micropolar (K) and Microrotational (λ) parameters delays the onset of stability. The result are in agreement with the works of other literature sited.
Źródło:
World Scientific News; 2019, 115; 174-192
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of kidney function changes in sea salt workers during harvest season in Thailand
Autorzy:
Luangwilai, T.
Robson, M.G.
Siriwong, W.
Powiązania:
https://bibliotekanauki.pl/articles/2083100.pdf
Data publikacji:
2022
Wydawca:
Narodowy Instytut Zdrowia Publicznego. Państwowy Zakład Higieny
Tematy:
heat exposure
agricultural work
kidney function change
Opis:
Background. Occupational factors have previously been mentioned as contributing to decreased kidney function and the development of chronic kidney disease of unknown cause. Sea salt workers are one of the occupations facing high outdoor temperatures and a highly, intensive workload. Objective. The purpose of the study was to examine whether the kidney function of sea salt workers at the beginning of the harvest season differs from kidney function at the end of the harvest season and to identify factors that can predict the change of kidney function. Material and methods. Data were collected from salt workers (n=50) who were between 18–60 years of age without hypertension, diabetes, and kidney disease in Samut Sakhon province, Thailand. Urine specific gravity (USG) was used for hydration status and the estimated glomerular filter rate (eGFR) was used to measure kidney function. The mixed model was used to find differences over the harvest season and prediction of factors. Results. On average, the eGFR was estimated to decrease by 15.2 ml/min/1.73 m2 over the harvest season. The decline in eGFR of sea salt workers with moderate and heavy workloads were significantly faster than their light workload counterparts after controlling for other covariates. Similarly, dehydration (USG ≥ 1.030) significantly accelerated the rate of kidney function loss. Conclusions. Our study confirmed exposure to heat over the harvest season leads to decreased eGFR in sea salt workers. The rate of change of eGFR could be predicted by workload and hydration status. Workers with dehydration who performed medium to heavy workloads in farms showed faster kidney function decline than those who performed light workload.
Źródło:
Roczniki Państwowego Zakładu Higieny; 2022, 73, 1
0035-7715
Pojawia się w:
Roczniki Państwowego Zakładu Higieny
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Memorandum of prof. A. K. Oppenheim and an example of application of the Oppenheim correlation (OPC)* for the heat losses during the combustion in IC-engine
Autorzy:
Jankowski, A.
Czerwinski, J.
Powiązania:
https://bibliotekanauki.pl/articles/246928.pdf
Data publikacji:
2010
Wydawca:
Instytut Techniczny Wojsk Lotniczych
Tematy:
combustion engines
Oppenheim Correlation OCP
heat transfer
heat looses
Vibe-Function
Opis:
The Oppenheim Correlation (OPC) is an empirical algorithm, which allows a simple estimate of heat losses to the wall during the combustion in IC-engine. In present paper the results ofdifferent applications of OPC will be shown. Even if there are still several needs and ideas for further research it can be stated, that the OPC is a promising possibility of modelling the wali heat losses and due to its simplicity it has to be recommended to the engine community. The OPC can be used not only for didactics purposes, but also for quick simulation of wall heat losses and eventuałły for the on-line regulation of the cooling system. In particular basic milestones of calculation of the working cycle, modelling of heat losses according to Oppenheim (OPC), engines and test procedure, examples of the OPC-application are presented in the paper. The OPC can be recommended to the engine community as a good alternative of modelling and calculation of the heat losses trough the combustion chamber wall.
Źródło:
Journal of KONES; 2010, 17, 2; 181-194
1231-4005
2354-0133
Pojawia się w:
Journal of KONES
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of heat exposure on dehydration and kidney function among sea salt workers in Thailand
Autorzy:
Luangwilai, T.
Robson, M.G.
Siriwong, W.
Powiązania:
https://bibliotekanauki.pl/articles/2082819.pdf
Data publikacji:
2021
Wydawca:
Narodowy Instytut Zdrowia Publicznego. Państwowy Zakład Higieny
Tematy:
heat exposure
dehydration
kidney function
agricultural work
Opis:
Background. Excessive heat exposure and dehydration among agricultural workers have been reported to reduce kidney function and lead to chronic kidney disease of unknown etiology (CKDu). Objective. This cross-sectional study aimed to assess heat exposure, factors related to dehydration and the relationship between dehydration and biomarkers of kidney function among sea salt workers in Thailand. Material and methods. Wet bulb globe temperature (WBGT) was used at the time workers started work outdoors on salt farms. Urine-specific gravity, urine osmolarity, and serum creatinine were collected from 50 workers after work. Results. The results showed that more than 50% of the participants were dehydrated after work. The maximum hours spent working per day was 10. The average water intake was 1.51 L. Urine specific gravity was highly significant correlated with urine osmolality (rs = 0.400, p<0.01), and urine osmolality was significantly correlated with the estimated glomerular filtration rate (eGFR) (rs = 0.349, p<0.05). In bivariate analysis adjusted for age, sex, and current alcohol consumption, we found that a WBGTTWA ≥ 30°C (OR = 0.08, 95% CI = 0.01-0.44, p = 0.003) and hours spent working (OR=2.22, 95% CI = 1.42-3.47, p <0.001) were independently associated with dehydration. This suggests that workers should increase their time spent on breaks and increase water consumption. Conclusions. Educational program on heat exposure and heat-related illness prevention strategies should be provided.
Źródło:
Roczniki Państwowego Zakładu Higieny; 2021, 72, 4; 435-442
0035-7715
Pojawia się w:
Roczniki Państwowego Zakładu Higieny
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heat conduction problem in a two-layered hollow cylinder by using the Greens function method
Autorzy:
Kukla, S.
Siedlecka, U.
Powiązania:
https://bibliotekanauki.pl/articles/122646.pdf
Data publikacji:
2013
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
heat conduction problem
two-layered cylinder
Green's function method
Opis:
In this paper, a solution of the heat conduction problem in a two-layered hollow cylinder by using the Green’s function method is presented. The considerations concern the heat conduction in the radial direction while taking into account time-dependent boundary conditions. The continuity condition of the temperature at the dividing surface of the layers is written in the form of a Volterra integral equation.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2013, 12, 2; 45-50
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of heat treatment on breakage rate function of ulexite
Autorzy:
Ipek, H.
Sahan, H.
Powiązania:
https://bibliotekanauki.pl/articles/110413.pdf
Data publikacji:
2013
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
ulexite
grinding
ball milling
breakage rate function
heat treatment
microwave
Opis:
The kinetics of batch grinding and heat treated of ulexite using different size fractions (–3350+2360, –2360+1700, –1700+1180, 1180+850, –850+600, –600+425, –425+300, –300+212 and – 212+150 micrometers was determined using a standard Bond ball mill. It was found that breakage of ulexite follows the first order behavior for all feed sizes with the correlation coefficients equal to approximately 98%. The dry grinding of the single-sized fraction and heat treatment of ulexite showed that heat treatment samples were ground much faster than the original ulexite samples.
Źródło:
Physicochemical Problems of Mineral Processing; 2013, 49, 2; 651-658
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phonon-Induced Thermodynamic Properties of Ultra-narrow Wires
Autorzy:
Ilić, D.
Šetrajčić, J.
Jaćimovski, S.
Powiązania:
https://bibliotekanauki.pl/articles/1029824.pdf
Data publikacji:
2018-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
Phonons
ultra-narrow wire
the Green function
thermodynamics
specific heat
Opis:
In this paper, we investigated the influence of size effect on thermodynamic properties of ultra-narrow wires with a simple cubic lattice, by means of two-time dependent Green functions method, adjusted to confined crystalline structures. Poles of Green functions, which defining phonon spectra, are found by solving the secular equation. For different boundary parameters, this problem is presented graphically. The temperature behavior of ultra-narrow wire thermal capacitance is compared to that of bulk structures. It turned out that in low-temperature region thermal capacitance of the ultra-narrow wire is notably lower than in the corresponding bulk sample. How this fact reflects the thermal, conducting and superconducting properties of materials, is discussed in the conclusion.
Źródło:
Acta Physica Polonica A; 2018, 133, 1; 57-62
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Soil heat flux and air temperature as factors of radon (Rn-222) concentration in the near-ground air layer
Autorzy:
Podstawczyńska, A.
Pawlak, W.
Powiązania:
https://bibliotekanauki.pl/articles/971505.pdf
Data publikacji:
2016
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
air temperature
Central Poland
exponential function
Rn-222
soil heat flux
Opis:
A unique, highly time-resolved, and synchronous three-year dataset of near-surface atmospheric radon-222 as well as soil heat flux and air temperature measurements at two sites (rural and urban) in Central Poland are investigated. The recognition of temporal variability of Rn-222 and selected meteorological variables in the urban and rural areas served to create two statistical models for estimation of this radionuclide concentration at 2 m a.g.l. The description of the relationships between the variables for individual months was established on the basis of an exponential function and an exponential function with time derivative of predictor to account for the hysteresis issue. The model with time derivative provided better results. The weakest fitting of modelled data to empirical ones is observed for the winter months. During subsequent seasons, air temperature as well as QG-driven (soil heat flux) models exhibited very high agreement with the empirical data (MBE, RMSE, MAE, and ‘index of agreement’ by Willmott were used to evaluate the models). A restriction in the use of QG for Rn-222 concentration was observed only in winter in the case of snow cover occurrence, which reduces the daily QG variability. A unique, highly time-resolved, and synchronous three-year dataset of near-surface atmospheric radon-222 as well as soil heat flux and air temperature measurements at two sites (rural and urban) in Central Poland are investigated. The recognition of temporal variability of Rn-222 and selected meteorological variables in the urban and rural areas served to create two statistical models for estimation of this radionuclide concentration at 2 m a.g.l. The description of the relationships between the variables for individual months was established on the basis of an exponential function and an exponential function with time derivative of predictor to account for the hysteresis issue. The model with time derivative provided better results. The weakest fitting of modelled data to empirical ones is observed for the winter months. During subsequent seasons, air temperature as well as QG-driven (soil heat flux) models exhibited very high agreement with the empirical data (MBE, RMSE, MAE, and ‘index of agreement’ by Willmott were used to evaluate the models). A restriction in the use of QG for Rn-222 concentration was observed only in winter in the case of snow cover occurrence, which reduces the daily QG variability.
Źródło:
Nukleonika; 2016, 61, 3; 231-237
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Nonexistence of global solutions for a nonlinear parabolic equation with a forcing term
Autorzy:
Alshehri, Aisha
Aljaber, Noha
Altamimi, Haya
Alessa, Rasha
Majdoub, Mohamed
Powiązania:
https://bibliotekanauki.pl/articles/29519396.pdf
Data publikacji:
2023
Wydawca:
Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
Tematy:
nonlinear heat equation
forcing term
blow-up
test function
differential inequalities
Opis:
The purpose of this work is to analyze the blow-up of solutions of a nonlinear parabolic equation with a forcing term depending on both time and space variables $ u_t − Δu = |x|^α |u|^p + \text{a} (t) \text{w} (x)$ for $ (t, x) ∈ (0,∞) × \mathbb{R}^N $, where $ α ∈ \mathbb{R}, p > 1 $, and $ \text{a} (t) $ as well as $ \text{w} (x) $ are suitable given functions. We generalize and somehow improve earlier existing works by considering a wide class of forcing terms that includes the most common investigated example $ t^σ \text{w} (x) $ as a particular case. Using the test function method and some differential inequalities, we obtain sufficient criteria for the nonexistence of global weak solutions. This criterion mainly depends on the value of the limit $ lim_{t \to \infty} \frac{1}{t} \int_0^t \text{a} (s) ds $. The main novelty lies in our treatment of the nonstandard condition on the forcing term.
Źródło:
Opuscula Mathematica; 2023, 43, 6; 741-758
1232-9274
2300-6919
Pojawia się w:
Opuscula Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transfer function–based impulse response analysis for a class of hyperbolic systems of balance laws
Autorzy:
Bartecki, K.
Powiązania:
https://bibliotekanauki.pl/articles/206531.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
hyperbolic system
balance law
transfer function
impulse response
Laplace transform
heat exchanger
Opis:
Results of the impulse response analysis for a class of dynamical systems, described by two weakly coupled linear partial differential equations of hyperbolic type, defined on a one-dimensional spatial domain are presented. For the case of two boundary inputs of the Dirichlet type, the analytical expressions for the impulse response functions are derived based on the inverse Laplace trans form of the 2×2 transfer function matrix of the system. The influence of the boundary inputs configuration on the impulse response functions is demonstrated. The considerations are illustrated with a practical example of a thin-walled double-pipe heat exchanger operating in parallel- and countercurrent-flow modes, which correspond to the analyzed boundary conditions.
Źródło:
Control and Cybernetics; 2015, 44, 3; 327-355
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Path planning for an autonomous underwater vehicle in a cluttered underwater environment based on the heat method
Autorzy:
Sun, Kaiyue
Liu, Xiangyang
Powiązania:
https://bibliotekanauki.pl/articles/1838198.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
autonomous underwater vehicle
path planning
heat method
heat diffusion
cost function
pojazd podwodny autonomiczny
planowanie trasy
dyfuzja ciepła
funkcja kosztu
Opis:
This paper proposes a novel autonomous underwater vehicle path planning algorithm in a cluttered underwater environment based on the heat method. The algorithm calculates the isotropic and anisotropic geodesic distances by adding the direction and magnitude of the currents to the heat method, which is named the anisotropy-based heat method. Taking account of the relevant influence of the environment on the cost functions, such as currents, obstacles and turn of the vehicle, an efficient collision-free and energy-optimized path solution can be obtained. Simulation results show that the anisotropy-based heat method is able to find a good trajectory in both static and dynamic clutter fields (including uncertain obstacles and changing currents). Compared with the fast marching (FM) algorithm, the anisotropy-based heat method is not only robust, flexible, and simple to implement, but it also greatly saves time consumption and memory footprint in a time-variant environment. Finally, the evaluation criteria of paths are proposed in terms of length, arrival time, energy consumption, and smoothness.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2021, 31, 2; 289-301
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Path planning for an autonomous underwater vehicle in a cluttered underwater environment based on the heat method
Autorzy:
Sun, Kaiyue
Liu, Xiangyang
Powiązania:
https://bibliotekanauki.pl/articles/1838202.pdf
Data publikacji:
2021
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
autonomous underwater vehicle
path planning
heat method
heat diffusion
cost function
autonomiczny pojazd podwodny
planowanie trasy
dyfuzja ciepła
funkcja kosztu
Opis:
This paper proposes a novel autonomous underwater vehicle path planning algorithm in a cluttered underwater environment based on the heat method. The algorithm calculates the isotropic and anisotropic geodesic distances by adding the direction and magnitude of the currents to the heat method, which is named the anisotropy-based heat method. Taking account of the relevant influence of the environment on the cost functions, such as currents, obstacles and turn of the vehicle, an efficient collision-free and energy-optimized path solution can be obtained. Simulation results show that the anisotropy-based heat method is able to find a good trajectory in both static and dynamic clutter fields (including uncertain obstacles and changing currents). Compared with the fast marching (FM) algorithm, the anisotropy-based heat method is not only robust, flexible, and simple to implement, but it also greatly saves time consumption and memory footprint in a time-variant environment. Finally, the evaluation criteria of paths are proposed in terms of length, arrival time, energy consumption, and smoothness.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2021, 31, 2; 289-301
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Energy, entropy and work function in a molecule with degeneracy
Autorzy:
Malaver, Manuel
Powiązania:
https://bibliotekanauki.pl/articles/1177950.pdf
Data publikacji:
2018
Wydawca:
Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
Tematy:
Statistical mechanics
degeneracy
entropy
heat capacity
internal energy
limit of high and low temperature
work function
Opis:
In this paper, we have deduced some thermodynamic properties for a molecular system with degeneracy based in the postulates of the statistical mechanics. We obtain analytical expressions for internal energy U, heat capacity Cv , entropy S and work function o Helmholtz free energy A. It is predicted in this research the thermodynamic behavior of U, Cv, S and A in the limit of high and low temperature.
Źródło:
World Scientific News; 2018, 97; 250-257
2392-2192
Pojawia się w:
World Scientific News
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The fundamental solutions to the central symmetric time-fractional heat conduction equation with heat absorption
Autorzy:
Povstenko, Y.
Klekot, J.
Powiązania:
https://bibliotekanauki.pl/articles/122778.pdf
Data publikacji:
2017
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
non-Fourier heat conduction
Caputo fractional derivative
heat absorption
Laplace integral transform
Fourier transform
Mittag-Leffler function
przewodzenie ciepła
pochodna ułamkowa Caputo
absorpcja ciepła
transformata Laplace'a
transformata Fouriera
funkcja Mittag-Lefflera
Opis:
The time-fractional heat conduction equation with heat absorption proportional to temperature is considered in the case of central symmetry. The fundamental solutions to the Cauchy problem and to the source problem are obtained using the integral transform technique. The numerical results are presented graphically.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2017, 16, 2; 101-112
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparison of heating curves of a rectangular busbar in different conditions of heat abstraction during the short-circuit heating
Autorzy:
Zaręba, M.
Powiązania:
https://bibliotekanauki.pl/articles/201224.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
analytical methods
field theory
transient heat flow
short-circuit in leads
Green’s function
metody analityczne
teoria pola
nieustalony przepływ ciepła
funkcja Greena
Opis:
The paper compares heating curves for a rectangular busbar in the conditions of convective and adiabatic heat transfer during short-circuit heating. Different coefficients of heat transfer from the external surface of the busbar and different busbar cross-sections have been assumed. This has allowed determining the error value occurring when the adiabatic rather than convective boundary condition is presumed at short circuit. The analysis takes into account a change of resistivity in the temperature function. The respective boundary-initial problems have been solved with analytical methods using Green’s function. The calculated results show that no considerable errors occur for long-lasting short circuits with an adiabatic rather than convective boundary condition.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2018, 66, 1; 79-85
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 20

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