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Tytuł:
Queueing system M/M/n/(m, V ) with non-identical servers
Autorzy:
Małek, J.
Ziółkowski, M.
Powiązania:
https://bibliotekanauki.pl/articles/121812.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Humanistyczno-Przyrodniczy im. Jana Długosza w Częstochowie. Wydawnictwo Uczelniane
Tematy:
queueing system
loss probability
system kolejkowy
prawdopodobieństwo straty
Opis:
We investigate multi-server queueing systems with Poisson arrivals, non-identical servers and customers of random volume, under assumption that customer’s service time having an exponential distribution doesn’t depend on his volume, but service time parameters can be different for different servers. We also assume that the total volume of customers present in the system at arbitrary time instant is bounded by some constant value V > 0. For such systems the stationary customers number distribution and loss probability are determined.
Źródło:
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics; 2013, 18; 29-39
2450-9302
Pojawia się w:
Scientific Issues of Jan Długosz University in Częstochowa. Mathematics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
M/M/n/(m,V) queueing systems with a rejection mechanism based on AQM
Autorzy:
Ziółkowski, M.
Małek, J.
Powiązania:
https://bibliotekanauki.pl/articles/122605.pdf
Data publikacji:
2013
Wydawca:
Politechnika Częstochowska. Wydawnictwo Politechniki Częstochowskiej
Tematy:
Markovian process
queueing systems with non-homogeneous customers
active queue management introduction
Opis:
M/M/n/(m,V) queueing systems with service time independent of customer volume are well known models used in computer science. In real computer systems (computer networks etc.) we often deal with the overload problem. In computer networks we solve the problem using AQM techniques, which are connected with introducing some accepting function that lets us reject in random way some part of the arriving customers. It causes reduction of each customer's mean waiting time and let us avoid jams in consequence. Unfortunately, in this way the loss probability increases. In this paper we investigate the analogous model based on some generalization of M/M/n/(m,V) queueing system. We obtain formulas for a stationary number of customers distribution function and loss probability and we do some computations in special cases.
Źródło:
Journal of Applied Mathematics and Computational Mechanics; 2013, 12, 1; 121-130
2299-9965
Pojawia się w:
Journal of Applied Mathematics and Computational Mechanics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Shape optimization in problems governed by generalised Navier-Stokes equations: existence analysis
Autorzy:
Haslinger, J.
Malek, J.
Stebel, J.
Powiązania:
https://bibliotekanauki.pl/articles/970130.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Badań Systemowych PAN
Tematy:
optimal shape design
paper machine headbox
incompressible non-Newtonian fluid
algebraic turbulence model
Opis:
We study a shape optimization problem for a paper machine headbox which distributes a mixture of water and wood fibers in the paper manufacturing process. The aim is to find a shape which a priori ensures the given velocity profile on the outlet part. The mathematical formulation leads to an optimal control problem in which the control variable is the shape of the domain representing the header, the state problem is represented by the generalised Navier-Stokes system with nontrivial boundary conditions. The objective of this paper is to prove the existence of an optimal shape.
Źródło:
Control and Cybernetics; 2005, 34, 1; 283-303
0324-8569
Pojawia się w:
Control and Cybernetics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Powder Metallurgy Preparation of Co-Based Alloys for Biomedical Applications
Autorzy:
Marek, I.
Novák, P.
Mlynár, J.
Vojtěch, D.
Kubatík, T.
Málek, J.
Powiązania:
https://bibliotekanauki.pl/articles/1402090.pdf
Data publikacji:
2015-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.Qp
62.20.F-
64.70.kd
Opis:
Co-based alloys represent very important group of materials used for medical applications. Currently, fabrication of these materials is preferentially done by casting or forming. Production by powder metallurgy techniques is less common. However, powder metallurgy fabrication of these alloys brings advantages such as reduced machining, possibility of alloying by high-melting elements, preparation of nanocrystalline materials with enhanced mechanical properties or producing of porous alloys with improved ability to integrate into issues. In this work, our attention was focused on fundamental preparation of an CoCrMo alloy by two methods of powder metallurgy. In the first method, pure metallic powders were mixed, pressed and sintered in vacuum furnace. The second applied technology consisted of mechanical alloying using planetary ball mill and compaction by spark plasma sintering technique. A series of samples was prepared under various conditions by these procedures. Dependence of microstructure, phase composition and mechanical properties of prepared samples on fabrication conditions (milling parameters, sintering temperature etc.) was studied. Obtained results were compared with properties of commercial cast cobalt alloy used for medical applications.
Źródło:
Acta Physica Polonica A; 2015, 128, 4; 597-601
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Determination of Phase Transformation Temperatures by Dilatometric Test of S960MC Steel
Autorzy:
Málek, M.
Mičian, M.
Moravec, J.
Powiązania:
https://bibliotekanauki.pl/articles/1837700.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
steel S960MC
dilatometric test
phase transformation temperatures
metallography
microstructure
stal S960MC
test dylatometryczny
temperatura przemian fazowych
metalografia
mikrostruktura
Opis:
The phenomenon of “soft zone” is occurring in the heat affected zone (HAZ) of high strength low alloy (HSLA) steels. Therefore, the process of weld metal solidification and phase transformation in HAZ is essential to understand the behaviour of the material, especially in the case where welded joints are debilitating part of the construction. The simulation program SYSWELD is powerful tool to predict solidification and phase transformation of welding joint, what correspond to the mechanical properties of the joints. To achieve relevant results of the simulation, it is necessary to use right mathematic-material model of the investigated material. Dilatometric test is the important methods to gather necessary input values for material database. In this paper is investigated physical and metallurgical properties of S960MC steel. The dilatometric curves were carried out on the laboratory machine dilatometer DIL 805L. In addition to determination of the phase transformation temperatures at eight levels of the cooling rate, the microstructure and hardness of the material are further analysed. The hardness of the samples reflects the achieved microstructure. Depending on the cooling rate, several austenitic transformation products were observed such as pearlite, bainite, martensite and many different ferritic microstructures. The differences between the transformation temperature results using the first derivation method and the three tangent method are up to 2%. The limit cooling rate was set at value 30°C/s. The microstructure consists only of bainite and marten site and the hardness reaches a value of 348HV and higher.
Źródło:
Archives of Foundry Engineering; 2021, 21, 2; 57-64
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optimizing the Lightweight Ceramic Proppants Properties
Autorzy:
Wisniewski, P.
Szymanska, J.
Malek, M.
Mizera, J.
Powiązania:
https://bibliotekanauki.pl/articles/1187431.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.20.-n
Opis:
The paper presents results of sintering proppants parameters and its influence on light ceramic proppants obtained by the mechanical granulation method. The proppants were prepared basing on a ceramic composition consisting of three raw materials such as kaolin, clay and bauxite mixed with poly(vinyl alcohol) binder with a molecular weight 26000 g/mol and hydrolysis degree of 88%, added in amount of 5 wt% with respect to the powder. Sintering temperature range oscillated between 1200 and 1225°C, kiln rotations were 1-2 rpm. Sintered proppants were characterized in compliance with PN-EN ISO 13503-2 norm and bulk density, sphericity coefficient, turbidity, solubility in acids and scanning electron microscopy observations have been estimated. The results demonstrated that sintering temperature and kiln rotation have an essential effect of the proppants parameters.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 501-503
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sylvicultural procedures in catchment areas of the mountain streams as exemplified by the Skrzyczne massif in Poland
Autorzy:
Malek, S.
Barszcz, J.
Majsterkiewicz, K.
Powiązania:
https://bibliotekanauki.pl/articles/38536.pdf
Data publikacji:
2014
Wydawca:
Instytut Badawczy Leśnictwa
Tematy:
catchment area
mountain stream
climatic zone
vegetation zone
Beskids Mountains
Skrzyczne massif
Polska
headwater
watercourse
Opis:
Extensive disintegration of spruce forests in the Beskidy Mts. in South Poland generates a need to regenerate sizeable areas as well as to rebuild forest stands which have defended themselves against breakdown. In practice, the magnitude of relevant management tasks does not allow for keeping up with the progressive destruction of forest, especially at higher altitudes, where natural regeneration does not occur as much as necessary. In addition, the species composition is limited to spruce, sometimes accompanied by beech and fir, whereas other species have a negligible share. What may be helpful in solving this problem is the method of regeneration of such areas and of establishment of under-canopy cultures, consisting of patchwork, multi-stage regeneration task performance, starting from the areas with the best chance of reforestation success and using the existing self-sown trees. Such areas undoubtedly include habitats with better water balance, i.e. humid habitats (in the case of larger areas, distinguished in the forest management plan as humid forest site types). The aim of the present study was to propose management of watercourses and headwater areas in the region of the Skrzyczne massif where the selected catchments are situated on the southern (the Malinowski Stream) and the northern (the Roztoka Czyrna stream) slopes of this massif. The research was carried out in August 2012 and included juxtaposition of available hydrological maps with actual field conditions along with identification of springs and streams and the course of their beds in order to update the existing data. The updating of the forest numerical maps in the existing databases of the State Forests IT System (SILP) included verification of the course of streams and determination of their nature (penament or periodic) with a division into the existing ones and the added ones. The data was recorded against the background of the division of the forest surface, contour lines, major roads, climate and plant floors and forest habitat types. The total length of streams was ascertained. The catchment areas and areas along their beds were determined by adopting variable distances from the beds, depending on climate and plant zones and the slope gradient. The adopted distances were: 5 m in the upper forest zone, 10 m in the middle forest zone, 20 m in the lower forest zone on both sides of the bed and in the headwater area within the radius of 10 m from a source. Specific sylvicultural procedures in headwater areas and in the neighbourhood of watercourses were described in each climatic and vegetation zones.
Źródło:
Folia Forestalia Polonica. Series A . Forestry; 2014, 56, 1
0071-6677
Pojawia się w:
Folia Forestalia Polonica. Series A . Forestry
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of the Basic Properties of Ceramic Proppants in Raw State Obtained by the Method of Mechanical Granulation
Autorzy:
Zarzycka, D.
Wisniewski, P.
Malek, M.
Szymanska, J.
Mizera, J.
Powiązania:
https://bibliotekanauki.pl/articles/1191748.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Je
Opis:
The investigation of fabricated ceramic materials, which can be used as proppants, is presented. Proppants are ceramic materials applied in hydraulic fracturing during extraction of shale gas. Solid slurry pumped with liquid into the deposit causes destruction of the rock structure. The role of proppants is to avoid closing of formed pores and as result enable gas migration from the deposit. Due to processing requirements and conditions in formations (high pressure and temperature), proppants should be characterized by proper physico-mechanical properties. The aim of this work was to elaborate the preparation method of ceramic materials, which can be used as proppants. In this paper results of properties studies of obtained proppants are presented. The influence of raw materials composition, especially the type of applied binder, was examined. Two types of green proppants obtained by the method of mechanical granulation without binder and with poly(vinyl alcohol) in amount of 5 wt% with respect to the powder were used. The properties: bulk density, roundness and sphericity coefficient, grain size and also structure and morphology of proppants was determined by the method of scanning electron microscopy with energy dispersive spectroscopy. The results indicate that composition of raw materials and type of binder have an important influence on the properties of obtained proppants in green state.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 552-555
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Element content of Scots pine (Pinus sylvestris L.) stands of different densities
Autorzy:
Skonieczna, J.
Malek, S.
Polowy, K.
Wegiel, A.
Powiązania:
https://bibliotekanauki.pl/articles/52511.pdf
Data publikacji:
2014
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Technologii Drewna
Tematy:
element content
Scotch pine
Pinus sylvestris
stand
different density
chemical diversity
nutrient
heavy metal
woody biomass
bark
branch
needle
Opis:
Modern forestry management should be based on the principle of sustainability.In order to preserve habitat productivity, the amount of nutrients removed from the environment along with forestry products must be taken into consideration. This study shows the exact concentrations of chemical elements in different tree parts of Scots pine, growing on poor soils in north-western Poland. The observedvalues were compared to the values found in literature. In addition, the relationship between the concentrations of elements and stem diameter or stand density was researched. The highest concentration of chemical elements was observed in the needles (C, N, P, K, Mg, S, Mn, Na, Fe) and the lowest (C, N, P, S, Cu, Na, Ni, Pb, Zn, Fe) in the stem wood. Most of the macronutrients (P, K, Ca, Mg and S) reached optimal values, with the exception of N showing a deficiency, especially in the needles. The relationship between the content of elements and DBH or stand density was rather weak, and in both cases, negative.
Źródło:
Drewno. Prace Naukowe. Doniesienia. Komunikaty; 2014, 57, 192
1644-3985
Pojawia się w:
Drewno. Prace Naukowe. Doniesienia. Komunikaty
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Technological Properties of Ceramic Slurries Based on Silicon Carbide with Poly(vinyl alcohol) Addition for Shell Moluds Fabrication in Precision Casting Process
Autorzy:
Malek, M.
Wisniewski, P.
Szymanska, J.
Mizera, J.
Kurzydlowski, K.
Powiązania:
https://bibliotekanauki.pl/articles/1186781.pdf
Data publikacji:
2016-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.05.Zx
Opis:
In this work technological properties of ceramic slurries based on silicon carbide powder with solid content 70 wt% were presented. These slurries were prepared for obtaining shell moulds in precision casting of Ni superalloys engine parts. The main binder was dispersion containing nanoalumina particles. Additionally poly(vinyl alcohol) with molecular weight 26000 g/mol as 5 wt% water solution was used as a rheological modifier. To characterize silicon carbide: scanning electron microscopy images, chemical composition, Zeta potential and grain size were studied. Technological properties of ceramic slurries i.e.: plate weight test, viscosity, dynamic viscosity, density and pH were investigated. Properties of silicon carbide based ceramic slurries are very promising and their shell moulds are very perspective for future application in aerospace industry.
Źródło:
Acta Physica Polonica A; 2016, 129, 4; 528-530
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Which one to choose multi focus or trade-off among competitive priorities? Evidence from finnish SMEs
Autorzy:
Timilsina, B.
Forsén, N.
Takala, J.
Malek, N. A.
Powiązania:
https://bibliotekanauki.pl/articles/407042.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
business environment
competitiveness
firm performance
competitive priority
sustainable competitive advantage
Opis:
This paper examines the relationship between business environment, competitiveness and firm performance considering a survey data from three consecutive years: 2013-2015. The comparative analysis showed that over these years business environment, competitiveness and firm performance of Finnish SMEs are slowly deteriorating. Results from correlation analysis revealed that business environment, competitiveness and firm performance are positively correlated. However, the relationships between these variables are not consistent in respect to competitive priorities indicating a dynamic nature of cost, quality, time, and flexibility dimensions. Besides these findings our analysis acknowledged that to improve firm performance, irrespective to the choice of competitive priority, SMEs should pay more attention to their competitiveness rather than blaming the business environment. The paper concludes that simultaneous use of competitive priority dimensions might be more favorable as a source of competitiveness and competitive advantage to improve firm performance. However, the managers are encouraged to compare the results, findings and concepts presented in this paper among themselves and comprehend the specific answer to the question posed in the title.
Źródło:
Management and Production Engineering Review; 2016, 7, 1; 77-88
2080-8208
2082-1344
Pojawia się w:
Management and Production Engineering Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Critical attributes on supply chain strategy implementation: case study in Europe and Asia
Autorzy:
Sillanpää, I.
binti Abdul Malek, N. A.
Takala, J.
Powiązania:
https://bibliotekanauki.pl/articles/407456.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
supply chain management
sense and respond
strategy implementation
Opis:
This case study research aims to compare the performance of the implementation of supply chain management (SCM) strategies within Asian and European Companies. The case study measures company’s opinions of supply chain strategy implementation through utilization of Sense and Response methodology. Critical Factor Index (CFI), Balanced Critical Factor Index (BCFI) and Scaled Critical Factor Index (SCFI) are used in this study to represent the result of comparison between European and Asian companies. From the analysis of comparison of all Sense and Response models, it can be concluded that there are differences and similarities of critical attributes that affecting supply chain strategy implementation in Asian and European companies. There are two attributes that have consistent trend for both regions; innovation and organization structure. In this research the analysis of supply chain strategy implementation was made for the needs of manufacturing industry. Suggestions for future research are multiple case studies in different industry areas in global business environment. The results provide a guideline to the company to measure the right attributes for making the right decision in a dynamic environment. It also provides good knowledge for companies to implement supply chain strategies, the main approaches to implement it and the main challenges in supply chain strategy implementation. Supply chain strategy implementation was analyzed in the European and Asian companies. This research shows that there are several developing areas for companies when implementing supply chain strategies.
Źródło:
Management and Production Engineering Review; 2013, 4, 4; 66-75
2080-8208
2082-1344
Pojawia się w:
Management and Production Engineering Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Technological Properties of SiC-Based Ceramic Slurries for Manufacturing Investment Casting Shell Moulds
Właściwości technologiczne mas lejnych na bazie SiC stosowanych do produkcji ceramicznych form odlewniczych
Autorzy:
Małek, M.
Wiśniewski, P.
Matysiak, H.
Zagórska, M.
Kurzydłowski, K.J.
Powiązania:
https://bibliotekanauki.pl/articles/356553.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
binders
investment casting
polyvinyl alcohol
SiC slurries
shell mould
spoiwa
odlewanie
alkohol poliwinylowy
masa lejna
forma odlewnicza
Opis:
In this work technological properties of ceramic slurries based on silicon carbide were characterized. Silicon carbide and poly(vinyl alcohol) in an amount 6%, 10% and 15 wt. % as a solution were added to prepare the ceramic slurries. Solid phase content in ceramic slurries was 62,5 wt.%. Plate weight test, pH, density, viscosity (measured by the Zhan 4# cup) and dynamic viscosity were investigated. Dipping test on wax model was done to measure adhesive properties. Characterization of SiC fillers powder was made by determination of grain size, density, chemical composition, Zeta potential and by use of scanning electron microscopy. Obtained results of ceramic slurries based on SiC meet standard specification in industrial investment casting and its properties are very promising for future application in investment casting of superalloys.
W artykule przedstawiono wyniki badań właściwości technologicznych mas ceramicznych na osnowie SiC mogących znaleźć zastosowanie do produkcji form odlewniczych do odlewania precyzyjnego części turbin lotniczych. Zawiesiny ceramiczne z SiC o stężeniu 62,5% otrzymano w mieszadle mechanicznym z dodatkiem 6, 10, 15% wag. alkoholu poli(winylowego) spełniającego rolę spoiwa oraz upłynniacza. Przeprowadzono szereg badań materiałoznawczych dla proszku, polimeru oraz wytworzonych mas lejnych, w tym lepkość względną i dynamiczną, pomiar gęstości, pH oraz zanurzeniowy test płyty. Pomiary prowadzono przez 96h. Udowodniono, iż właściwości technologiczne oraz reologiczne ceramicznych mas pozwalają na zastosowanie ich do produkcji form odlewniczych przeznaczonych do procesów odlewania precyzyjnego części turbin lotniczych.
Źródło:
Archives of Metallurgy and Materials; 2014, 59, 3; 1059-1062
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Supplementary irrigation at container nursery
Autorzy:
Durlo, G.
Jagiello-Lenczuk, K.
Kormanek, M.
Malek, S.
Banach, J.
Powiązania:
https://bibliotekanauki.pl/articles/45462.pdf
Data publikacji:
2018
Wydawca:
Instytut Badawczy Leśnictwa
Tematy:
water balance
forest
seedling
nursery
Scotch pine
Norway spruce
oak
European beech
forest tree
seedling production
climate condition
forestry
Źródło:
Leśne Prace Badawcze; 2018, 79, 1
1732-9442
2082-8926
Pojawia się w:
Leśne Prace Badawcze
Dostawca treści:
Biblioteka Nauki
Artykuł
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