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    Wyświetlanie 1-6 z 6
    Tytuł:
    Mining deployment optimization
    Optymalizacja rozmieszczenia wyposażenia w kopalniach
    Autorzy:
    Čech, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/219660.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    rozmieszczenie wyposażenia
    planowanie kopalni
    optymalizacja
    programowanie liniowe
    system wspomagający podejmowanie decyzji
    deployment problem
    mine planning
    optimizing
    linear programming
    decision support system
    Opis:
    The deployment problem, researched primarily in the military sector, is emerging in some other industries, mining included. The principal decision is how to deploy some activities in space and time to achieve desired outcome while complying with certain requirements or limits. Requirements and limits are on the side constraints, while minimizing costs or maximizing some benefits are on the side of objectives. A model with application to mining of polymetallic deposit is presented. To obtain quick and immediate decision solutions for a mining engineer with experimental possibilities is the main intention of a computer-based tool. The task is to determine strategic deployment of mining activities on a deposit, meeting planned output from the mine and at the same time complying with limited reserves and haulage capacities. Priorities and benefits can be formulated by the planner.
    Podobnie jak w wojskowości, problem rozmieszczenia wyposażenia pojawia się w wielu gałęziach przemysłu, w tym także górnictwie. Reguły decyzyjne określają jak rozmieścić określone czynności w przestrzeni aby uzyskać pożądane rezultaty w sposób zapewniający zgodność z określonymi wymogami, zapewniający dotrzymanie limitów narzuconych przez ograniczenia, a ponadto by zminimalizować koszty lub maksymalizować korzyści. Przedstawiono model mający zastosowanie do wydobycia złoża metali. Głównym założeniem odpowiedniego narzędzia komputerowego jest dostarczanie inżynierom górnictwa natychmiastowego rozwiązania decyzyjnego z możliwością eksperymentowania. Zadanie polega na określeniu rozmieszczenia czynności górniczych w obrębie złoża, tak by spełnić założenia odnośnie wielkości wydobycia, jednocześnie biorąc pod uwagę ograniczenia mocy przerobowych systemów transportowych, na pierwszym miejscu stawiając zakładane priorytety i korzyści, co jest zadaniem planistów.
    Źródło:
    Archives of Mining Sciences; 2016, 61, 3; 461-471
    0860-7001
    Pojawia się w:
    Archives of Mining Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Evaluation of porosity in Al alloy die castings
    Autorzy:
    Říhová, M.
    Cech, J.
    Havlíčková, J.
    Powiązania:
    https://bibliotekanauki.pl/articles/382450.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    stop AlSi9Cu3
    odlewnictwo
    kadłub silnika
    porowatość
    wielkość mechaniczna
    symulacja
    AlSi9Cu3 alloy
    casting
    engine block
    porosity
    mechanical values
    simulation
    Opis:
    Mechanical properties of an Al-alloy die casting depend significantly on its structural properties. Porosity in Al-alloy castings is one of the most frequent causes of waste castings. Gas pores are responsible for impaired mechanical-technological properties of cast materials. On the basis of a complex evaluation of experiments conducted on AlSi9Cu3 alloy samples taken from the upper engine block which was die-cast with and without local squeeze casting it can be said that castings manufactured without squeeze casting exhibit maximum porosity in the longitudinal section. The area without local squeeze casting exhibits a certain reduction in mechanical properties and porosity increased to as much as 5%. However, this still meets the norms set by SKODA AUTO a.s.
    Źródło:
    Archives of Foundry Engineering; 2012, 12, 1; 93-98
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of compound deoxidation of steel with Al, Zr, rare earth metals, and Ti on properties of heavy castings
    Autorzy:
    Senberger, J.
    Cech, J.
    Zadera, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/382459.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    odlewanie stali
    odtlenianie
    odlew ciężki
    steel casting
    deoxidation
    conchoidal fractures
    heavy casting
    Opis:
    Heavy steel castings deoxidized with aluminium are sometimes brittle intercrystalline failed during their service along primary grain boundaries what is initiated by aluminium nitrides and so called conchoidal fractures are formed. The tendency to forming the conchoidal fractures depends in particular on cooling rate (the casting modulus), aluminium and nitrogen contents in steel. During deoxidation, when manufacturing heavy castings, the elements with high affinity to nitrogen, zirconium or titanium, are added to steel that would decrease nitrogen activity by the bond on stable nitrides. The formation of stable nitrides should reduce the tendency of steel to the formation of conchoidal fractures. Deoxidation was thermodynamically analyzed at presence of the mentioned elements. For particular conditions a probable course of deoxidation was estimated at test castings. The deoxidation course was checked by microanalysis of deoxidation products (inclusions). For service and experimental castings the anticipated composition of inclusions was compared. It has been proved that in heavy castings with high aluminium contents in steel under studied conditions neither the addition of zirconium nor of titanium nor of rare earth metals will prevent the formation of conchoidal fractures.
    Źródło:
    Archives of Foundry Engineering; 2012, 12, 1; 99-104
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Prediction of the Mechanical Properties of Chrome-Nickel Austenitic Stainless Steels with Respect to their Chemical Composition
    Autorzy:
    Záděra, A.
    Maroš, B.
    Blažík, P.
    Čech, J.
    Kaňa, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/379648.pdf
    Data publikacji:
    2018
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    austenitic steels
    planned experiment
    mechanical properties
    regression analysis
    stale austenityczne
    eksperyment
    właściwości mechaniczne
    analiza regresji
    Opis:
    The research was concerned with the influence of chemical composition of austenitic steels on their mechanical properties. Resulting properties of castings from austenitic steels are significantly influenced by the solidification time that affects the size of the primary grain as well as the layout of elements within the dendrite and its parts with regard to the last solidification points in the interdendritic melt. During solidification an intensive segregation of all admixtures occurs in the melt, which causes a whole range of serious metallurgical defects and it has also a significant influence on subsequent precipitation of carbides and intermetallic phases. Chemical heterogeneity then affects the structure and mechanical properties of the casting. In a planned experiment, we cast melted steels containing 18 to 28 % Cr and 8 to 28 % Ni with variable carbon and nitrogen contents. Testing the tensile strength of the cast specimens we could determine the Rp0.2, Rm, and A5 values. The dependence of the mechanical properties on the chemical content was described by regression equations. The planned experiment results allow us to control the chemical content for the given austenitic steel quality to achieve the required values of the mechanical properties.
    Źródło:
    Archives of Foundry Engineering; 2018, 18, 1; 217-221
    1897-3310
    2299-2944
    Pojawia się w:
    Archives of Foundry Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Mechanical and Thermal Properties of Individual Phases Formed in Sintered Tungsten-Steel Composites
    Autorzy:
    Matějíček, J.
    Nevrlá, B.
    Čech, J.
    Vilémová, M.
    Klevarová, V.
    Haušild, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/1402135.pdf
    Data publikacji:
    2015-10
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    62.20.-x
    65.40.-b
    Opis:
    Tungsten is a prime candidate material for plasma facing components in fusion devices, thanks to its advantageous properties with respect to interaction with hot plasma. For its bonding to the supporting structure, composites and graded layers can be used for the reduction of stress concentration at the interface. When tungsten and steel are processed at elevated temperatures, e.g. hot pressing or spark plasma sintering, intermetallic phases may form and their presence and properties will affect the properties of the composite. In this work, mechanical and thermal properties of the individual phases, i.e. steel, tungsten and Fe-W intermetallics are investigated. Mechanical properties were determined by instrumented indentation. Thermal conductivity was determined by the xenon flash method on a range of samples with varying composition, from which the conductivities of each constituent were estimated. The results can be used for the optimization of compositional profiles and processing conditions for manufacturing of plasma facing components.
    Źródło:
    Acta Physica Polonica A; 2015, 128, 4; 718-721
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Physical activity and body composition of 5 to 7 years old children
    Autorzy:
    Junger, J.
    Palanska, A.
    Cech, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/2052249.pdf
    Data publikacji:
    2014
    Wydawca:
    Akademia Bialska Nauk Stosowanych im. Jana Pawła II w Białej Podlaskiej
    Tematy:
    preschool child
    body composition
    physical activity
    obesity
    norms
    Opis:
    Current exercise prescription and physical activity guidelines recommend preschool children to perform at least 60 minutes of moderate to vigorous structured physical activity and at least 60 minutes of unstructured physical activity every day. The purpose of this study was to extend knowledge about the volume of physical activity in 5- to 7-year-old children in relation to their body composition. Also, we recorded the course of growth changes and physical activity levels in 6-year-old children in the previous half century. The sample consisted of 69 pre-school age children (5 - 7 years) attending selected kindergartens located in the area of Presov self-governing region. Of 69 children, 36 were girls and 33 were boys. The volume and intensity of physical activity performed by children during their stay in kindergartens was measured using heart rate monitoring system POLAR Team 2 Pro. Body composition was assessed using direct segmental multi-frequency bioelectric impedance analysis (DSM-BIA) device InBody 230. Parameters of somatic development corresponding with the secular trend are disproportionate to children’s physical activity, which is considered to be an irreplaceable factor underlying health of children. However, the physical activity levels of children are decreasing. The volume of physical activity does not meet the minimum standard recommended by NASPE (Prokopec et al. 1986) and average intensity of physical activity expressed by heart rate does not reach the medium intensity zone.
    Źródło:
    Health Problems of Civilization; 2014, 08, 3; 12-19
    2353-6942
    2354-0265
    Pojawia się w:
    Health Problems of Civilization
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-6 z 6

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