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Tytuł:
An automatic hybrid method for retinal blood vessel extraction
Autorzy:
Yang, Y.
Huang, S.
Rao, N.
Powiązania:
https://bibliotekanauki.pl/articles/907899.pdf
Data publikacji:
2008
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
naczynie krwionośne
ekstrakcja
obraz
siatkówka
morfologia matematyczna
grupowanie rozmyte
blood vessel extraction
retinal image
mathematical morphology
fuzzy clustering
Opis:
The extraction of blood vessels from retinal images is an important and challenging task in medical analysis and diagnosis. This paper presents a novel hybrid automatic approach for the extraction of retinal image vessels. The method consists in the application of mathematical morphology and a fuzzy clustering algorithm followed by a purification procedure. In mathematical morphology, the retinal image is smoothed and strengthened so that the blood vessels are enhanced and the background information is suppressed. The fuzzy clustering algorithm is then employed to the previous enhanced image for segmentation. After the fuzzy segmentation, a purification procedure is used to reduce the weak edges and noise, and the final results of the blood vessels are consequently achieved. The performance of the proposed method is compared with some existing segmentation methods and hand-labeled segmentations. The approach has been tested on a series of retinal images, and experimental results show that our technique is promising and effective.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2008, 18, 3; 399-407
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Approximation by Szász type operators including Sheffer polynomials
Autorzy:
Rao, N.
Wafi, A.
Deepmala, A.
Powiązania:
https://bibliotekanauki.pl/articles/950884.pdf
Data publikacji:
2017
Wydawca:
Politechnika Rzeszowska im. Ignacego Łukasiewicza. Oficyna Wydawnicza
Tematy:
Szász operators
Sheffer polynomials
Voronovskaya type theorem
operatory Szásza
wielomiany Sheffera
twierdzenie typu Woronowskiej
Opis:
In present article, we discuss voronowskaya type theorem, weighted approximation in terms of weighted modulus of continuity for Szász type operators using Sheffer polynomials. Lastly, we investigate statistical approximation for these sequences.
Źródło:
Journal of Mathematics and Applications; 2017, 40; 135-148
1733-6775
2300-9926
Pojawia się w:
Journal of Mathematics and Applications
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Theoretical investigation of stresses induced at blade mounting locations in steam turbine rotor system
Autorzy:
Prasad, D. K.
Ramana, K. V.
Rao, N. M.
Powiązania:
https://bibliotekanauki.pl/articles/947280.pdf
Data publikacji:
2019
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
tarcza wirnika
wirnik turbiny parowej
naprężenie styczne
rotor disc
radial stress
tangential stress
steam turbine rotors
Opis:
One of the most common incipient losses of integrity in mechanical structures is the development and propagation of cracks. Especially in rotating members like steam turbine rotors etc. cracks, because of their potential, cause catastrophic failures and are a grave threat to an uninterrupted operation and performance. A crack may propagate from some small imperfections on the surface of the body or inside of the material and it is most likely to appear in correspondence to high stress concentration. Crack propagation path is generally determined by the direction of maximum stress or by the minimum material strength. Hence determination of stresses induced has been the focus of attention for many researchers. In the present work, development of a mathematical model to determine the stresses induced in a rotating disc of varying thickness is studied. This model is applied to a steam turbine rotor disc to determine the induced stresses and radial deflection. The mathematical modeling results are validated with the results obtained using Ansys package. The results of the present study will be useful in diagnosing the location and magnitude of maximum stress induced in the turbine rotor disc and stress intensity factor due to the presence of crack.
Źródło:
International Journal of Applied Mechanics and Engineering; 2019, 24, 2; 295-307
1734-4492
2353-9003
Pojawia się w:
International Journal of Applied Mechanics and Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Inferential Issues in Model-Based Small Area Estimation: Some New Developments
Autorzy:
Rao, J. N. K.
Powiązania:
https://bibliotekanauki.pl/articles/465725.pdf
Data publikacji:
2015
Wydawca:
Główny Urząd Statystyczny
Tematy:
area level models
complex parameters
informative sampling
model misspecification
robust estimation
unit level models
Opis:
Small area estimation (SAE) has seen a rapid growth over the past 10 years or so. Earlier work is covered in the author's book (Rao 2003). The main purpose of this paper is to highlight some new developments in model-based SAE since the publication of the author's book. A large part of the new theory addressed practical issues associated with the model-based approach, and we present some of those methods for area level and unit level models. We also briefly mention some new work on synthetic estimation of area means or totals based on implicit models.
Źródło:
Statistics in Transition new series; 2015, 16, 4; 491-510
1234-7655
Pojawia się w:
Statistics in Transition new series
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Study on Creep Behavior of Composite Solid Propellants Using the Kelvin-Voigt Model
Autorzy:
Bihari, B. K.
Rao, N. P. N.
Gupta, M.
Murthy, K. P. S.
Powiązania:
https://bibliotekanauki.pl/articles/358395.pdf
Data publikacji:
2017
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
mechanical properties
viscoelasticity
propellant
creep
DMA
Opis:
A Kelvin-Voigt model consisting of a spring and a dashpot in parallel was applied for the viscoelastic characterization of solid rocket propellants. Suitable values of spring constants and damping coefficients were employed by a least squares fit of the errors to generate creep curves using a Dynamic Mechanical Analyzer (DMA) for composite solid propellants. Three different composite propellant formulations based on HTPB/AP/Al having burning rates of 5 mm/s, 15 mm/s and 20 mm/s were tested under different stress levels varying from 0.1 MPa to 3 MPa and at different temperatures varying from 35 °C to 85 °C. Creep behavior with recovery was studied and analyzed to evaluate the viscoelastic properties. The change in spring constants, representing elastic deformation, was very small compared to the damping coefficients for the propellants studied. For a typical propellant formulation, when the stress level was increased, the spring and damping coefficient both increased significantly whereas for an increase in temperature, they remained nearly constant. However, the ratio E/η was observed to be constant and independent of stress level. It was also observed that the variation of E and η varied linearly with increase in stress whereas their ratio showed a logarithmic variation. A mathematical correlation was developed to evaluate the viscoelastic properties during creep of composite propellants.
Źródło:
Central European Journal of Energetic Materials; 2017, 14, 3; 742-756
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Comparative performance with different versions of low heat rejection combustion chambers with crude rice bran oil
Porównanie osiągów różnych wersji komór spalania o małych stratach ciepła przy wykorzystaniu surowego oleju roślinnego z otrąb ryżowych
Autorzy:
Murali, K. M. V. S.
Rao, N. D. P.
Prasad, B. A.
Murthy, P. V. K.
Powiązania:
https://bibliotekanauki.pl/articles/140033.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
alternate fuels
vegetable oil
biodiesel
LHR engine
fuel performance
exhaust emissions
combustion characteristics
paliwa alternatywne
olej roślinny
silnik o małych stratach ciepła
wydajność paliwa
emisja spalin
charakterystyka spalania
Opis:
It has been found that the vegetable oils are promising substitute, because of their properties are similar to those of diesel fuel and they are renewable and can be easily produced. However, drawbacks associated with crude vegetable oils are high viscosity, low volatility call for low heat rejection combustion chamber, with its significance characteristics of higher operating temperature, maximum heat release, and ability to handle lower calorific value (CV) fuel etc. Experiments were carried out to evaluate the performance of an engine consisting of different low heat rejection (LHR) combustion chambers such as ceramic coated cylinder head-LHR-1, air gap insulated piston with superni (an alloy of nickel) crown and air gap insulated liner with superni insert – LHR-2; and ceramic coated cylinder head, air gap insulated piston and air gap insulated liner – LHR-3 with normal temperature condition of crude rice bran oil (CRBO) with varied injector opening pressure. Performance parameters (brake thermal efficiency, brake specific energy consumption, exhaust gas temperature, coolant load, and volumetric efficiency) and exhaust emissions [smoke levels and oxides of nitrogen [NOx]] were determined at various values of brake mean effective pressure of the engine. Combustion characteristics [peak pressure, time of occurrence of peak pressure, maximum rate of pressure rise] were determined at full load operation of the engine. Conventional engine (CE) showed compatible performance and LHR combustion chambers showed improved performance at recommended injection timing of 27 degrees bTDC and recommend injector opening pressure of 190 bar with CRBO operation, when compared with CE with pure diesel operation. Peak brake thermal efficiency increased relatively by 7%, brake specific energy consumption at full load operation decreased relatively by 3.5%, smoke levels at full load decreased relatively by 11% and NOx levels increased relatively by 58% with LHR-3 combustion chamber with CRBO at an injector opening pressure of 190 bar when compared with pure diesel operation on CE.
Jak wiadomo, oleje roślinne są obiecującym substytutem paliw ropopochodnych, ponieważ ich właściwości są podobne do oleju dieslowskiego, są odnawialne i łatwe do wyprodukowania. Niemniej, surowe oleje roślinne wykazują wady, takie jak wysoka lepkość i mała lotność, co wymaga komory spalania o małych stratach ciepła, której istotnymi cechami są m.in. wyższa temperatura robocza, maksymalne wydzielanie ciepła i zdolność do wykorzystania paliwa o mniejszej wartości kalorycznej (CV). Przeprowadzono eksperymenty mające na celu ocenę osiągów silnika z różnymi komorami spalania o małych stratach ciepła (LHR), takich jak głowica cylindra o pokryciu ceramicznym (LHR-1), tłok izolowany szczeliną powietrzną z denkiem ze stopu Superni (superstop niklu) i tuleją cylindra z wkładką z Superni izolowaną szczeliną powietrzną (LHR-2) oraz głowica cylindra z pokryciem ceramicznym, tłok i tuleja cylindra izolowane szczelinami powietrznymi (LHR-3). Badania prowadzono przy normalnej temperaturze oleju roślinnego (surowy olej z otrąb ryżowych, CRBO) i zmiennym ciśnieniu w otworze wtryskiwacza. Parametry osiagów silnika (użyteczna sprawność termiczna, użyteczny współczynnik zużycia energii, temperatura gazu wydychanego, obciążenie obiegiem chłodziwa i współczynnik napełnienia) oraz emisje wydechowe [poziomy dymu i tlenków azotu, NOx] zostały wyznaczone przy różnych wartościach średniego użytecznego ciśnienia w silniku. Charakterystyki spalania [ciśnienie szczytowe, czas występowania ciśnienia szczytowego, maksymalna szybkość wzrostu ciśnienia] zostały wyznaczone w warunkach pracy silnika z pełnym obciążeniem. W porównaniu z silnikiem napędzanym olejem diesla, silnik konwencjonalny (CE) wykazał podobne osiągi przy pracy z olejem roślinnym (CRBO), a w komorach spalania o małych stratach ciepła (LHR) uzyskano lepsze osiągi przy zalecanym kącie wtrysku 27b stopni TDC (przed górnym punktem zwrotnym) i zalecanym ciśnieniu w otworze wtryskiwacza równym 190 bar. Szczytowa użyteczna sprawność cieplna wzrosła relatywnie o 7%, użyteczny współczynnik zużycia energii zmalał o 3,5% przy pracy z pełnym obciążeniem, poziomy dymu przy pełnym obciążeniu zmalały o 11%, a poziom tlenków NOx wzrósł relatywnie o 58% w przypadku komory spalania typu LHR-3 napędzanej olejem roślinnym CBRO przy ciśnieniu w otworze wtryskiwacza 190 bar, w porównaniu z parametrami uzyskanymi przy pracy z czystym olejem diesla.
Źródło:
Archive of Mechanical Engineering; 2014, LXI, 4; 627-651
0004-0738
Pojawia się w:
Archive of Mechanical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Comparison of Small Area Estimation Methods for Poverty Mapping
Autorzy:
Guadarrama, María
Molina, Isabel
Rao, J. N. K.
Powiązania:
https://bibliotekanauki.pl/articles/465671.pdf
Data publikacji:
2016
Wydawca:
Główny Urząd Statystyczny
Tematy:
area level model
non-linear parameters
empirical best estimator
hierarchical Bayes
poverty mapping
unit level models
Opis:
We review main small area estimation methods for the estimation of general nonlinear parameters focusing on FGT family of poverty indicators introduced by Foster, Greer and Thorbecke (1984). In particular, we consider direct estimation, the Fay-Herriot area level model (Fay and Herriot, 1979), the method of Elbers, Lanjouw and Lanjouw (2003) used by the World Bank, the empirical Best/Bayes (EB) method of Molina and Rao (2010) and its extension, the Census EB, and finally the hierarchical Bayes proposal of Molina, Nandram and Rao (2014). We put ourselves in the point of view of a practitioner and discuss, as objectively as possible, the benefits and drawbacks of each method, illustrating some of them through simulation studies.
Źródło:
Statistics in Transition new series; 2016, 17, 1; 41-66
1234-7655
Pojawia się w:
Statistics in Transition new series
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Understanding the Effect of Multiple Traverse Feed during Friction Stir Welding Processes
Autorzy:
Shailesh Rao, A.
Yuvaraja, N.
Powiązania:
https://bibliotekanauki.pl/articles/352033.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
friction stir welding
multiple pass of tool
microstructre
tensile strength
Opis:
The scope of this paper is to understand the effect of multiple pass of the tool during friction stir welding process of Al-17Si alloy and evaluate its microstructure and tensile strength. The rotational speed of 900 rpm with three different feed rates (50, 100, 150 mm/min) was selected for this process. The weld gap seen below the tool tip has been reduced drastically during the multiple pass and after the third pass the weld gap was invisible. With the increase in the feed rate, the adhesion was reduced between the tool pin circumference and diffused material, hence a small increase in the weld gap was observed. The substantiate changes in the microstructure was observed due to the severe formation of the metal during low feed rate. With the increase in the feed rate, some coarse grains were observed near and below the tool pin. The tensile strength during the multiple pass of the tool was studied and found better for lower feed rate. Further, the variation of the tool speeds (600, 900 and 1200 rpm) for constant feed rates of 100 mm/min were discussed. The more heat input improves plunging depth thereby reduces weld gap, but for higher heat input (tool rotation: 1200 rpm; feed rate: 100mm/min) increase in weld gaps was seen. The tensile properties for all the cases were discussed. The diffusion process, friction force and relative velocity pertaining to this process were highlighted finally.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 1; 203-210
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A step toward a universal theory of failure handling
Autorzy:
Obeid, N.
Rao, R.B.
Powiązania:
https://bibliotekanauki.pl/articles/328519.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Polskie Towarzystwo Diagnostyki Technicznej PAN
Tematy:
logika
monitoring
czas
rozumowanie
diagnozowanie
podejmowanie decyzji
uszkodzenie
logic
failure
reasoning
decision-making
learning
diagnosis
time
event
nonmonotonic
Opis:
We explore, in this paper, some of the fundamental requirements needed for a Universal Theory of Failure Handling. We shall show that dealing with failure touches on our reasoning, predictive, evaluative and judgmental capabilities and thus it requires the ability to reason with incomplete and uncertain temporal information. It also requires reasoning with events before they even happen and about the effect of actions for as long as these are relevant, even if the available time does not permit. There may also be a need for reasoning about the reasoning process itself. We shall discuss the notion of failure with respect to decision-making and knowledge. We give a very brief presentation of Dorner's logic of failure and research into artificial intelligence and its implication for handling failures. We shall propose means of computing the degrees of failure induced by humans and in physical systems. In addition, we shall initiate a discussion on reasoning with failures and put forward a proposal for an integrative and proactive approach to monitoring, diagnosis and learning from failures.
Źródło:
Diagnostyka; 2007, 1(41); 5-14
1641-6414
2449-5220
Pojawia się w:
Diagnostyka
Dostawca treści:
Biblioteka Nauki
Artykuł
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