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Tytuł:
Statistical analysis and modeling of SIP traffic for parameter estimation of server hysteretic overload control
Autorzy:
Abaev, P.
Razumchik, R.
Uglov, I.
Powiązania:
https://bibliotekanauki.pl/articles/308261.pdf
Data publikacji:
2013
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
Markov Modulated Poisson Process
overload control
SIP server
statistical analysis
Opis:
The problem of overload control in Session Initiation Protocol (SIP) signaling networks gives rise to many questions which attract researchers from theoretical and practical point of view. Any mechanism that is claimed to settle this problem down demands estimation of local (control) parameters on which its performance is greatly dependent. In hysteretic mechanism these parameters are those which define hysteretic loops. In order to find appropriate values for parameters one needs adequate model of SIP traffic flow circulating in the network under consideration. In this paper the attempt is made to address this issue. Analysis of SIP traffic collected from telecommunication operator’s network is presented. Traffic profile is built. It is shown that fitting with Markov Modulated Poisson Process with more than 2 phases is accurate. Estimated values of its parameters are given.
Źródło:
Journal of Telecommunications and Information Technology; 2013, 4; 22-31
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Statistical Analysis of Message Delay in SIP Proxy Server
Autorzy:
Abaev, P.
Razumchik, R.
Uglov, I.
Powiązania:
https://bibliotekanauki.pl/articles/958112.pdf
Data publikacji:
2014
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
single hop delay
SIP server
statistical analysis
waiting time
Opis:
Single hop delay of SIP message going through SIP proxy server operating in carriers backbone network is being analyzed. Results indicate that message sojourn times inside SIP server in most cases do not exceed order of tens of milliseconds (99% of all SIP-I messages experience less than 21 ms of sojourn delay) but there were observed very large delays which can hardly be attributed to message specic processing procedures. It is observed that delays are very variable. Delay components distribution that is to identied are not exponentially distributed or nearly constant even per message type or size. The authors show that measured waiting time and minimum transit time through SIP server can be approximated by acyclic phase-type distributions but accuracy of approximation at very high values of quantiles depends on the number outliers in the data. This nding suggests that modeling of SIP server with queueing system of GjPHjc type may server as an adequate solution.
Źródło:
Journal of Telecommunications and Information Technology; 2014, 4; 79-87
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Evaluation of human thermal comfort and heat stress in an outdoor urban setting in summer under arid climatic conditions
Autorzy:
Abdel-Ghany, A. M.
Al-Helal, I. M.
Shady, M. R.
Powiązania:
https://bibliotekanauki.pl/articles/950038.pdf
Data publikacji:
2014
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
arid regions
sensory perception
thermal comfort
climatic conditions
effective temperature
human thermal comfort
solar-radiation fluxes
thermal stress
heat stress
suchy klimat
percepcja sensoryczna
komfort cieplny
warunki klimatyczne
temperatura efektywna
komfort cieplny człowieka
strumienie promieniowania słonecznego
stres termiczny
stres cieplny
Opis:
Thermal sensation and heat stress potential were evaluated in summer in an outdoor arid environment. Such evaluation had never been made in arid regions. Various scales: the temperaturehumidity index (THI), physiological effective temperature (PET), universal thermal climatic index (UTCI) and standard effective temperature (SET*) were used for the evaluation. RayMan software model was used to estimate the PET and SET* and the UTCI-calculator was used for UTCI. The required air dry and wet bulb temperatures (Td, Tw), solar radiation flux (S0) and wind speed (V) were measured in summer (April 29–July 15). The results showed that: Persons are exposed to strong heat stress and would feel very hot most of the day time; and they are safe from heat stress risk and would feel comfortable most of the night time. Heat stress levels can be determined using the PET or UTCI scales; both are valid for arid environment and their results are almost similar; however, the THI cannot be used. SET* index specifically describes the thermal sensations and discomfort conditions along with summer days at any activity under arid conditions.
Źródło:
Environment Protection Engineering; 2014, 40, 3; 139-150
0324-8828
Pojawia się w:
Environment Protection Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bank’s performance and its determinants : evidence from Middle East, Indian sub-continent and African banks
Wydajność banku i jej determinanty : przykład Bliskiego Wschodu, indyjskich podwykonawczych oraz afrykańskich banków
Autorzy:
Abdul Hadi, A. R.
Hussain, H. I.
Suryanto, T.
Yap, T. H.
Powiązania:
https://bibliotekanauki.pl/articles/404815.pdf
Data publikacji:
2018
Wydawca:
Politechnika Częstochowska
Tematy:
bank’s liquidity
return on assets
capital adequacy ratio
non-performing loans
loan growth
static panel data
random effect model
credit creation theory of banking
płynność banku
zwrot z aktywów
współczynnik adekwatności kapitałowej
niespłacone pożyczki
wzrost pożyczek
statyczne dane panelowe
model losowego efektu
działalność kredytowa
Opis:
This study is driven by a motivation to examine the key determinants of bank’s performance as proxied by bank’s liquidity (LR), non-performing loans (NPL), capital adequacy ratio (CAR), loan growth (FEXP) and default risk premium (FQL) within the framework of credit creation theory of banking. Using random effect model as an estimation tool on 93 banks in Middle East, Africa and Indian subcontinent over study period from 2009 through 2016, the findings reveal that there are significant relationships between bank’s performance and its loan growth. Both ROA and FEXP are also found to be positively correlated. In contrast, the NPL and CAR are found to be negatively correlated with ROA. As a whole, it is evident that loan growth plays a very important role in supporting bank’s long term performance.
Celem badania jest przeanalizowanie kluczowych czynników determinujących wyniki banku w zależności od jego płynności (LR), zagrożonych kredytów (NPL), współczynnika wypłacalności (CAR), wzrostu kredytów (FEXP) i premii za ryzyko niewypłacalności (FQL) w ramach teorii bankowej dotyczącej działalności kredytowej. Jako narzędzie oceny, w 93 bankach na Bliskim Wschodzie, w Afryce i na subkontynencie indyjskim, w okresie od 2009 r. do 2016 r. wykorzystano model efektu losowego. Wyniki pokazują, że istnieją istotne zależności między wydajnością banku a zwiększeniem aktywności kredytowej. Na podstawie przeprowadzonych badań stwierdzono, że zarówno ROA, jak i FEXP są skorelowane dodatnio, natomiast NPL i CAR są skorelowane ujemnie z ROA. Reasumując, należy stwierdzić, że zwiększenie aktywności kredytowej odgrywa bardzo ważną rolę we wspieraniu długoterminowej wydajności banku.
Źródło:
Polish Journal of Management Studies; 2018, 17, 1; 17-26
2081-7452
Pojawia się w:
Polish Journal of Management Studies
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Biomedical Optical Applications of Liquid Crystal Devices
Autorzy:
Abdulhalim, I.
Moses, R.
Sharon, R.
Powiązania:
https://bibliotekanauki.pl/articles/1814044.pdf
Data publikacji:
2007-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.30.Va
42.70.Df
42.81.Gs
Opis:
Liquid crystals exhibit large electro-optic effects which make them useful for a variety of applications as fast, compact, and tunable spectral filters, phase modulators, polarization controllers, and optical shutters. They were largely developed for liquid crystal displays and in the last decade for optical telecommunications, however their application in the field of optical imaging just started to emerge. These devices can be miniaturized thus have a great potential useful in miniature optical imaging systems for biomedical applications. Using a collection of tunable phase retarders one can perform: 1. Stokes parameters imaging for skin and eye polarimetric imaging; 2. Tunable filtering to be used for hyperspectral imaging, fluorescence microscopy, and frequency domain optical coherence tomography; 3. Adaptive optical imaging and eye aberrations correction; 4. Phase shift interferometric imaging; 5. Variable frequency structured illumination microscopy. Basic optics of liquid crystals devices is reviewed and some novel designs are presented in more detail when combined to imaging systems for a number of applications in biomedical imaging and sensing.
Źródło:
Acta Physica Polonica A; 2007, 112, 5; 715-722
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Approximation of a Solidification Problem
Autorzy:
Aboulaich, R.
Haggouch, I.
Souissi, A.
Powiązania:
https://bibliotekanauki.pl/articles/908072.pdf
Data publikacji:
2001
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
optymalizacja
metoda elementów skończonych
Stefan problem
free boundary
shape optimization
Euler method
finite element method
Opis:
A two-dimensional Stefan problem is usually introduced as a model of solidification, melting or sublimation phenomena. The two-phase Stefan problem has been studied as a direct problem, where the free boundary separating the two regions is eliminated using a variational inequality (Baiocci, 1977; Baiocchi et al., 1973; Rodrigues, 1980; Saguez, 1980; Srunk and Friedman, 1994), the enthalpy function (Ciavaldini, 1972; Lions, 1969; Nochetto et al.., 1991; Saguez, 1980), or a control problem (El Bagdouri, 1987; Peneau, 1995; Saguez, 1980). In the present work, we provide a new formulation leading to a shape optimization problem. For a semidiscretization in time, we consider an Euler scheme. Under some restrictions related to stability conditions, we prove an L^2-rate of convergence of order 1 for the temperature. In the last part, we study the existence of an optimal shape, compute the shape gradient, and suggest a numerical algorithm to approximate the free boundary. The numerical results obtained show that this method is more efficient compared with the others.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2001, 11, 4; 921-955
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Role of epigenetic mechanisms in plant response to low temperature
Autorzy:
Achrem, M.
Skuza, A.
Kalinka, A.
Szucko, I.
Filip, E.
Slominska-Walkowiak, R.
Rogalska, S.M.
Powiązania:
https://bibliotekanauki.pl/articles/19428.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Opis:
Plants are continuously exposed to various environmental stresses and they respond to them in different ways. Ambient temperature is among the most important environmental cues that directly influence plant growth and yield. Research in recent years has revealed that epigenetic mechanisms play a key role in plants' response to temperature stress. Changes in gene expression evoked by stress signals follow post-translational histone modifications, DNA methylation, histone variant incorporation, and the action of chromatin remodeling factors and Polycomb group proteins. The majority of epigenetic modifications induced by temperature stress are reversible in nature; thus, chromatin returns to its previous state after the stress has passed. Some modifications seem stable, however, due presumably to so-called stress memory. Epigenetic modifications can be inherited through mitosis and meiosis. By dint of epigenetic memory, plants can more efficiently respond to future stressful conditions, thereby increasing their potential for environmental adaptation. Recognition of the epigenetic mechanisms that take part in plants' response to changes of ambient temperature will increase our understanding of adaptations to stress conditions.
Źródło:
Acta Biologica Cracoviensia. Series Botanica; 2012, 54, 1
0001-5296
Pojawia się w:
Acta Biologica Cracoviensia. Series Botanica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Managerial approaches of environmental projects : an empirical study
Menedżerskie podejścia do projektów środowiskowych : badanie empiryczne
Autorzy:
Adamisin, P.
Kotulic, R.
Mura, L.
Kravcakova Vozarova, I.
Vavrek, R.
Powiązania:
https://bibliotekanauki.pl/articles/405253.pdf
Data publikacji:
2018
Wydawca:
Politechnika Częstochowska
Tematy:
cluster analysis
cophenetic correlation coefficient
environmental projects
regional differentiation
structural fund
sustainable planning
analiza skupień
współczynnik korelacji kofenetycznej
projekty środowiskowe
regionalne zróżnicowanie
fundusz strukturalny
zrównoważone planowanie
Opis:
The accession of Slovakia into the European Union significantly supported the possibility to participate in financial programs focused on different areas of social and economic spheres, financed substantially from EU sources. One of the subsidy areas has been the environmental protection. Due to the specifics of environmental projects, the irretrievable disposition of this financial aid is inevitable in many cases. This article analyses the spatial distribution of environmental projects financed from relevant subsidy schemes in individual regions of Slovakia. We can recognize that there is no significant close correlation between the economic development of a territory and the support through implemented projects.
Przystąpienie Słowacji do Unii Europejskiej dało możliwość uczestnictwa w programach finansowych skoncentrowanych na różnych sferach społecznych i gospodarczych, finansowanych w znacznej mierze ze środków UE. Jednym z obszarów dotacji była ochrona środowiska. Ze względu na specyfikę projektów środowiskowych, dysponowanie tą pomocą finansową jest w wielu przypadkach nieuniknione. Artykuł analizuje rozmieszczenie przestrzenne projektów środowiskowych finansowanych z odpowiednich programów subsydiowania w poszczególnych regionach Słowacji. Można uznać, że nie ma istotnej ścisłej korelacji między rozwojem gospodarczym danego terytorium a wsparciem za pośrednictwem realizowanych projektów.
Źródło:
Polish Journal of Management Studies; 2018, 17, 1; 27-38
2081-7452
Pojawia się w:
Polish Journal of Management Studies
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Measurement and evaluation of timber yields and corresponding non-timber forest products of selected tree species. An exploratory study on poplar, Acacia, Ulmus and Juglans tree species in Kyrgyzstan
Autorzy:
Agbenowu, Y.I.S.
Attah, R.
Powiązania:
https://bibliotekanauki.pl/articles/2049706.pdf
Data publikacji:
2018
Wydawca:
Fundacja na Rzecz Młodych Naukowców
Tematy:
forest zone
Kirgizstan
timber yield
wood measurement
evaluation
poplar
Acacia
Ulmus
Juglans
biomass
volume
net present value
growth yield
rotation age
Opis:
With issues of high timber demand and illegal logging in the forest zones of Kyrgyzstan, agroforestry may serve as a viable option for rectification. Yields of timber and expected income from the most popular tree species are in most cases lacking. The goal of this study is to evaluate the timber yields and non-timber forest product from Ulmus, Poplar, Acacia and Juglans tree species in Kyrgyzstan. More focus was allocated to Poplar as this is one of the most common and preferred tree species in Kyrgyzstan. A sample size of 420 trees was recorded from 18 stands with 20 trees measured in each stand with the exception of Juglans which were 6 stands with 9-17 trees each The study estimated (i) tree volume using allometric parameters (ii) age-biomass relationship (iii) Factual Branch Analysis model to estimate the above ground biomass of the different tree segments (iii) revenue deduction and NPV of Poplar trees and (iv) biological rotation Age to determine the suitable age for Poplar harvesting. The findings show that NPV is highest at 10 years for Poplar when it is being considered for fast-growing timber. The biological rotation age was, however, higher at around 17 years. Site-specific age-biomass model appears to be suitable for estimating tree biomass since the tree allometry was found to differ significantly between studied stands even with similar age ranges. The developed relationship and tree database can adequately be applied to estimate tree volume and biomass in similar site conditions in the studied region.
Źródło:
Environment, Earth and Ecology; 2018, 2, 1; 12-27
2543-9774
2451-4225
Pojawia się w:
Environment, Earth and Ecology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Controlling continuous bioreactor via nonlinear feedback: modelling and simulations approach
Autorzy:
Aguilar-López, R.
Neria-González, I.
Powiązania:
https://bibliotekanauki.pl/articles/200156.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
nonlinear feedback
sulfate-reducing process
continuous bioreactors
Lyapunov stability
nieliniowe sprzężenie zwrotne
proces redukcji siarczanu
bioreaktor
metoda Lapunowa
Opis:
The aim of this work is to present a class of nonlinear controller with an exponential-type feedback in order to regulate the sulfate mass concentration via the input flow in a continuous stirred tank bioreactor of an anaerobic sulfate-reducing process. The corresponding kinetic terms in the bioreactor’s modeling are modeled by unstructured modeling approach, which was experimentally corroborated. A sketch of proof of the closed-loop stability of the considered system is done under the framework of Lyapunov theory. Numerical experiments are conducted to show the performance of the proposed methodology in comparison with a well-tuned sigmoid controller.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2016, 64, 1; 235-241
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of luteolin on spermatological parameters, apoptosis, oxidative stress rate in freezing rabbit semen
Autorzy:
Akarsu, S.A.
Acısu, T.C.
Güngör, İ.H.
Çakır Cihangiroğlu, A.
Koca, R.H.
Türk, G.
Sönmez, M.
Gür, S.
Fırat, F.
Esmer Duruel, H.E.
Powiązania:
https://bibliotekanauki.pl/articles/16647483.pdf
Data publikacji:
2023
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
rabbit
semen
cryopreservation
luteolin
oxidative stress
apoptosis
Opis:
The aim of the present study was to determine the effects of Luteolin (LUT) on semen quality, oxidative stress, apoptosis, acrosomal integrity, mitochondrial membrane potential and dead sperm ratio in rabbits. Ejaculates from six New Zealand rabbits were collected, evaluated and pooled. The pooling was divided into five groups as control (no additive) LUT 25 μM, LUT 50 μM, LUT 100 μM and LUT 200 μM and LUT added. It was then filled into a falcon tube with Tris-based extender at a final concentration of approximately 35 x 106 spermatozoa. Diluated rabbit semen samples were drawn into frozen and thawed. Frozen semen straws were thawed at 37°C in 30 seconds. According to our findings, no statistical difference was found between all doses of luteolin and the control group in the CASA (computer assisted sperm analysis) analysis performed at 4°C. However, total motility, progressive motility and rapid sperm percentage were found to be higher in the frozen and thawed rabbit semen at a dose of LUT 50 μM compared to the other groups (p<0.05). While amplitude of lateral head displacement (ALH) and beat cross-frequency (BCF) values were found at the lowest dose of LUT 200 μM, a statistically significant difference was observed between the other groups. When the flow cytometry results were examined, no statistical difference was found between the rate of dead sperm, acrosomal integrity, mitochondrial membrane potential and apoptosis rate. Morever, the H2O2 percentage was found to be lower in all experimental groups compared to the control group (p<0.001). In conclusion, the addition of LUT in long-term storage of rabbit semen provided a protective effect for spermatozoa with its antioxidative properties against damage caused by cryopreservation.
Źródło:
Polish Journal of Veterinary Sciences; 2023, 26, 1; 91-98
1505-1773
Pojawia się w:
Polish Journal of Veterinary Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł

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