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1
Content available remote Scaling behavior of earthquakes’ inter-events time series
100%
Shadkhoo S. , Ghanbarnejad F. , Jafari G. , Tabar M.
Open Physics
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2009
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tom 7
|
nr 3
620-623
EN
In this paper, we investigate the statistical and scaling properties of the California earthquakes’ inter-events over a period of the recent 40 years. To detect long-term correlations behavior, we apply detrended fluctuation analysis (DFA), which can systematically detect and overcome nonstationarities in the data set at all time scales. We calculate for various earthquakes with magnitudes larger than a given M. The results indicate that the Hurst exponent decreases with increasing M; characterized by a Hurst exponent, which is given by, H = 0:34 + 1:53/M, indicating that for events with very large magnitudes M, the Hurst exponent decreases to 0:50, which is for independent events.
2
Content available remote A simplified methodology for scaling hydrodynamic data from Lagisza 460 MWesupercritical CFB boiler
100%
Mirek P.
Chemical and Process Engineering
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2011
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tom 32
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nr 4
245-253
EN
The paper presents the results of model studies on the hydrodynamics of the world's first supercritical circulating fluidized bed boiler Lagisza 460 MWe, carried out on a scale model built in a scale of 1/20 while preserving the full geometrical similarity. To reflect the macroscopic pattern of flow in the boiler's combustion chamber, tests were carried out based on two dimensionless flow dynamic similarity criteria, while maintaining a constant Froude number value between the commercial and the scaled-down units. A mix of polydispersion solids with its fractional composition determined by scaling down the particle size distribution of the boiler's inert material was utilised for the tests using a special scaling function. The obtained results show very good agreement with the results of measurements taken on the Lagisza 460 MWe supercritical CFB boiler.
3
Content available remote The influence of sampling point on solids suspension density applied in scaling of the hydrodynamics of a supercritical CFB boiler
100%
Mirek P. , Ziaja J.
Chemical and Process Engineering
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2011
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tom 32
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nr 4
391-399
EN
The article presents the results of laboratory tests carried out on a scaling model of the 966MWth fluidised-bed boiler operating in the Lagisza Power Plant, made on a scale of 1:20 while preserving the geometrical similarity. The tests were carried out for scaled-down material taken from different locations on the circulation contour in the state of full boiler loading. To reflect the hydrodynamic conditions prevailing in the combustion chamber, solids with properly selected density and particle size distribution were used. The obtained results have made it possible to determine the location for taking the most representative granular material sample.
4
Content available remote Scaling of flow phenomena in circulating fluidized bed boilers
100%
Mirek P.
Chemical and Process Engineering
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2011
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tom 32
|
nr 2
91-100
EN
The paper presents an overview of scaling models used for determining hydrodynamic parameters of Circulating Fluidized Bed boilers. The governing equations and the corresponding dimensionless numbers are derived and presented for three different approaches to the scaling law of fluidized beds: classical dimensional analysis, differential equations and integrated solutions and experimental correlations. Some results obtained with these equations are presented. Finally, the capabilities and limitations of scaling experiments are discussed.
5
Content available remote Scaling diminution by heterogeneous crystallization in a filtration element integrated with membrane distillation module
100%
Gryta M.
Polish Journal of Chemical Technology
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2009
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tom 11
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nr 2
60-65
EN
Water desalination by membrane distillation is restricted by calcium carbonate precipitation on the membrane surface, what resulted in a progressive decline of the permeate flux. The module rinsing by HCl solution removed this deposit, however, such operation could cause the membrane wettability, associated with lowering of the permeate flux. This phenomenon was inhibited when the membrane modules with prefiltration element, assembled directly at the inlet to module, were used. The salt deposits were formed mainly on the surface of the filtration element (nets area constituted over 10% of the membranes area), what protected the membranes assembled inside the module. The filter efficiency decreased when the deposit layer covered the entire surface of pre-filter element, and after a few hours (period of 10-20 h) the formation of crystallite on the membrane surface was also observed. Therefore, the formed deposit was systematically removed (at every 5 h) from this pre-filter by 3 wt.% HCl solutions. The periodical rinsing of nets by acid did not have a negative influence on the membrane
6
Content available remote Scaling features of ambient noise at different levels of local seismic activity. A case study for the Oni seismic station
100%
Matcharashvili T. , Chelidze T. , Javakhishvili Z. , Zhukova N.
Acta Geophysica
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2012
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tom Vol. 60, no. 3
809-832
EN
Investigation of dynamical features of ambient seismic noise is one of the important scientific and practical research challenges. We investigated scaling features of the ambient noises at the Oni seismic station, Georgia, using detrended fluctuation analysis method. Data from this seismic station, located in the epicentral zone of Oni M6.0, 2009, earthquake, were selected to include time periods with different levels of local seismic activity. It was shown that the investigated ambient noise is persistent longrange correlated at calm seismic conditions in the absence of earthquakes. Fluctuation features of the analyzed ambient noises were affected by local earthquakes, while remote seismic activity caused just slight quantitative changes. Processes related to the preparation of a strong local earthquake may cause quantifiable changes in fluctuation features of ambient noises. Fluctuation features of seismic noise for periods of increased local seismic activity cease to be long-range correlated and appear to become a complicated mixture of random and correlated behaviours.
7
Content available remote Assessment of Hand Function Through the Coordination of Contact Forces in Manipulation Tasks
88%
Jaric S. , Uygur M.
Journal of Human Kinetics
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2013
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tom 36
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nr 1
5-160
EN
Exploration of force coordination has been one of the most often used approaches in studies of hand function. When holding and manipulating a hand-held object healthy individuals are typically able to highly coordinate the perpendicular (grip force; GF) with the tangential component of the contact force (load force; LF). The purpose of this review is to present the findings of our recent studies of GF-LF coordination. Regarding the mechanical factors affecting GF-LF coordination, our data suggest that both different hand segments and their particular skin areas could have markedly different friction properties. It also appears that the absolute, rather than relative safety margin (i.e., how much the actual GF exceeds the minimum value that prevents slipping) should be a variable of choice when assessing the applied magnitude of GF. The safety margin could also be lower in static than in free holding tasks. Regarding the involved neural factors, the data suggest that the increased frequency, rather than an increased range of a cyclic LF could have a prominent detrimental effect on the GF-LF coordination. Finally, it appears that the given instructions (e.g., 'to hold' vs. 'to pull') can prominently alter GF-LF coordination in otherwise identical manipulation tasks. Conversely, the effects of handedness could be relatively week showing only slight lagging of GF in the non-dominant, but not in the dominant hand. The presented findings reveal important aspects of hand function as seen through GF-LF coordination. Specifically, the use of specific hand areas for grasping, calculation of particular safety margins, the role of LF frequency (but not of LF range) and the effects of given instructions should be all taken into account when conducting future studies of manipulation tasks, standardizing their procedures and designing routine clinical tests of hand function.
8
Content available remote Crackling noise in a discrete element model of single crack propagation
88%
Timár G. , Kun F.
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2011
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tom Vol. 11, No. 2
309-314
EN
We study the crackling noise emerging during single crack propagation obtained by discrete element modelling (DEM) in a specimen under three-point bending conditions. Analyzing temporal and spatial correlations of local breakings we show that the crack proceeds in bursts, which are characterized by power law distributions of their size and of the waiting times between consecutive events. We obtain a generic scaling form which describes crackling noise in materials with different degrees of heterogeneity. The results are in a good agreement with acoustic emission measurements in three-point bending experiments.
PL
W pracy badano odgłos pękania występujący podczas propagacji pojedynczego pęknięcia w proce poddawanej trzypunktowemu zginaniu, symulowanemu za pomocą metody elementów dyskretnych (ang. Discrete element method - DEM). Analiza czasowych i przestrzennych zależności lokalnego pękania wykazała, że pęknięcie postępuje przez rozdzielenie, co charakteryzuje się prawem potęgowym opisującym rozmiar szczelin oraz czasy przerw między kolejnymi etapami pękania. Opracowano ogólną postać skalowania, które opisuje odgłos pękania w materiałach o różnym stopniu niejednorodności. Uzyskane wyniki są zgodne z pomiarami emisji akustycznej w próbie trzypunktowego zginania.
9
Tranzystor - 60 lat minęło i co dalej?
63%
Jakubowski A. , Łukasiak L.
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2008
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tom R. 81, nr 5
666-671
PL
Przedstawiono historię elektroniki półprzewodnikowej ze szczególnym uwzględnieniem tranzystora MOS, trudności związane z dalszą miniaturyzacją, możliwe kierunki rozwoju oraz wybrane ograniczenia fundamentalne.
EN
The papers briefly presents the history of semiconductor electronics with emphasis on MOS transistor, difficulties associated with further miniaturization, possibile directions of development and selected fundamental limitations.
10
Content available remote Weryfikacja metody skalowania parametrów geometryczno-wytrzymałosciowych na modelach wirtualnych.
63%
Rutkowski J.
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2006
|
tom R. 79, nr 10
822-825
PL
Metoda skalowania parametrów geometryczno-wytrzymałościowych została opracowana w związku z potrzebą skrócenia czasu przygotowania modelu i obliczeń optymalizacyjnych konstrukcji mechanicznych. Zaletą metody skalowania jest szybkość uzyskiwania wyników, którą osiąga się dzięki przyjętym uproszczeniom i przybliżeniom. Te ostatnie są jednak źródłem niedokładności obliczeniowych, które należało zbadać. W tym celu prowadzone są badania symulacyjne, których pierwszy etap już zakończono, a wyniki przedstawiono.
EN
Presented are the results of simulation exercise carried out for veryfication of the presumed theoretical method of scaling of the strength/geometric parameters.
11
Content available remote Best Practices in Cluster Management
63%
Friedman R.
|
2006
|
tom Vol. spec. issue
25-28
EN
Albert Einstein defined success as ten percent inspiration and ninety percent perspiration. Although he had no inkling for the emergence of Linux Clusters for High Performance Computing (HPC) his words are ring true for designing, building and managing compute clusters. This paper focuses on best practices in implementing Cluster Management software, a paradigm for designing, building and managing compute clusters. The learnings are based on the successful experiences of environments using Scali’s leading Cluster Management solution, Scali Manage.
12
Content available Statistical damage mechanics - constitutive relations
51%
Rinaldi A. , Krajcinovic D. , Mastilovic S.
|
2006
|
tom Vol. 44 nr 3
585-602
EN
The statistical damage model presented by the authors in the previous paper of this series is used to formulate analytical constitutive relations for the hardening and softening phases of two-dimensional lattices. A proper definition of the damage parameter for the softening is introduced. The results confirm that the analytical model can be used for the study of the softening phase and failure. This research offers a seminal basis for Damage Tolerance Principles technology standards of the commercial airplane industry.
PL
Statystyczny model uszkodzenia, przedstawiony przez autorów w innej pracy, zastosowano tu do sformułowania analitycznych związków konstytutywnych w zakresie wzmocnienia i osłabienia dla dwuwymiarowych modeli sieciowych. Wprowadzono odpowiednią definicję parametru uszkodzenia w zakresie osłabienia. Uzyskane wyniki potwierdzają, że wprowadzony model analityczny można stosować do badania osłabienia i zniszczenia materiałów. Praca stanowić może podstawę do ustalenia norm technicznych uszkodzenia stosowanych w przemyśle lotniczym.
13
IRT i pomiar edukacyjny
51%
Kondratek B. , Pokropek A.
Edukacja
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2013
|
nr 4(124)
42–66
EN
Item response theory (IRT) is a family of statistical tools used to model relationships between item response and student ability. IRT models achieve this by parameterisation of item properties and distribution of the ability variable among students. This article presents a general introduction to the unidimensional IRT model, the most commonly used for dichotomously scored items (1PLM, 2PLM, 3PLM). Polytomously scored items and student ability estimation are also described. This article aims at introducing the reader to the technical aspects of IRT modelling in educational measurement and presents a range of practical applications. The article describes the analysis of complex research designs, test linking and equating, adaptive testing and item mapping as examples.
PL
Pod nazwą „item response theory” kryje się rodzina narzędzi statystycznych wykorzystywanych do modelowania odpowiedzi na rozwiązywane zadania oraz umiejętności uczniów. Modele IRT czynią to poprzez wprowadzenie parametryzacji, która określa: właściwości zadań oraz rozkład poziomu umiejętności uczniów. W artykule przedstawiony zostanie ogólny opis jednowymiarowego modelu IRT, przybliżone zostaną najczęściej stosowane modele dla zadań ocenianych dwupunktowo (2PLM, 3PLM, 1PLM) oraz wielopunktowo (GPCM), a także zarysowana zostanie problematyka estymacji poziomu umiejętności. Artykuł ma za zadanie wprowadzić czytelnika w techniczne szczegóły związane z modelowaniem IRT oraz przedstawić wybrane zastosowania praktyczne w pomiarze edukacyjnym. Wśród zastosowań praktycznych omówiono wykorzystanie IRT w analizie skomplikowanych schematów badawczych, zrównywaniu/łączeniu wyników testowych, adaptatywnym testowaniu oraz przy tworzeniu map zadań.
14
Content available remote Watermarking for images based on color manipulation and block subdivision
51%
Battiato S. , Castorina A.
|
2000
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tom Vol. 6, no 1-2
29-38
EN
In this paper we present a new watermarking scheme for color images. The method represents an improvement and a loose variation of the work done in [l, 2], where the authors proposed to alter the colors of a given image in an imperceptible way. Despite the theoretical accuracy of the method, an intensive testing has shown the weakness against some common image processing techniques in particular: JPEG compression, scaling and low-pass filtering. Experimental results will be produced, in order to demonstrate the validity of our new approach.
15
Content available Scaling of flow phenomena in circulating fluidized bed boilers
32%
Mirek P.
|
|
nr 2
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