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Wyświetlanie 1-15 z 49
Tytuł:
The thermal-flow behavior of the working chamber in an oil-free scroll compressor
Autorzy:
Rak, J.
Powiązania:
https://bibliotekanauki.pl/articles/240088.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
CFD
scroll
mesh deformation
spirala
deformacja siatek
Opis:
The paper presents the full transient, two-dimensional finite volume method numerical calculations of the classical involute scroll compressor geometry. The purpose of the study was to develop and evaluate an adaptable implementation of numerical fluid mechanics and thermodynamics modeling procedure with a mesh deformation. The methodology consisting in the compression chamber geometry preparation, mesh generation and governing equations solving was described. The evaluation was carried by simulating an adiabatic compression process and the results were compared with the theoretical zero-dimensional model and the existing research concerning the scroll chamber computational fluid dynamics modeling. It has been shown that the proposed modeling routine results in good accuracy for the scroll compressors study applications.
Źródło:
Archives of Thermodynamics; 2013, 34, 3; 161-172
1231-0956
2083-6023
Pojawia się w:
Archives of Thermodynamics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Proposal for water supply systems evaluation due to diversification of water intakes and water tanks
Autorzy:
Rak, J.
Boryczko, K.
Powiązania:
https://bibliotekanauki.pl/articles/95916.pdf
Data publikacji:
2018
Wydawca:
Fundacja Ekonomistów Środowiska i Zasobów Naturalnych
Tematy:
water supply
diversification
water intake
water tank
allocation
zaopatrzenie w wodę
dywersyfikacja
pobór wody
zbiornik wodny
przydział
Opis:
The aim of the study was to compare the various water supply systems – from rural to agglomerations, in terms of continuity of water supply to the inhabitants in a crisis situation. The work included the diversification of water intakes with their number and the maximum daily production capacity and the diversification of water in the water tanks, knowing their number and volume. RB1 and RB2 diversification indexes have been proposed. Assessment criteria were included with comment. The research component is a two-parameter assessment of diversification for selected water supply systems using the indicators proposed by the authors. The use of proprietary indicators to assess the diversification of water supply using preference functions gives the ability to perform calculations easily and accurately.
Źródło:
Ekonomia i Środowisko; 2018, 3; 63-70
0867-8898
Pojawia się w:
Ekonomia i Środowisko
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
End-to-end service survivability under attacks on networks
Autorzy:
Molisz, W.
Rak, J.
Powiązania:
https://bibliotekanauki.pl/articles/308000.pdf
Data publikacji:
2006
Wydawca:
Instytut Łączności - Państwowy Instytut Badawczy
Tematy:
survivable data networks
attacks on networks
scale-free networks
routing
resource allocation
Opis:
Network survivability is a capability of a networked system to provide its services despite failures or attacks. Attacks, e.g., due to acts of war, being potentially damaging events, were basically considered in the historical definitions of a survivability phenomenon. The meaning of the term: "network survivability" evolved in the last decade. Recently, attacks replayed the important role again. Their nature, however, including intrusions, probes, denials of service, differs from the old one. Survivability is strongly related to other fields of study. In particular, quality of service depends on network survivability. We investigate these dependencies in scale-free networks. Many networks are scale-free, i.e., their node degree distribution follows the power law. Nodes of the highest degrees, called centers, are highly vulnerable to attacks. Elimination of these nodes seriously degrades the overall performance of network services. In this paper we propose a model, which, based on traffic parameters of a demand, like delay or bit rate, allows to establish the survivable and attack proof end-to-end connections. The key idea of this model is that for the significant traffic, it establishes paths, which omit centers. The important connections become more resistant to attacks. We show that in the best case, obtained for the highest class of service, the number of broken connections is reduced even by factor 3. Example results are compared to those for the standard distance metrics. Our model is applicable to many network architectures and many classes of service.
Źródło:
Journal of Telecommunications and Information Technology; 2006, 3; 19-26
1509-4553
1899-8852
Pojawia się w:
Journal of Telecommunications and Information Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis and evaluation of hazards in emergency situations in water supply systems
Autorzy:
Boryczko, K.
Rak, J.
Powiązania:
https://bibliotekanauki.pl/articles/96825.pdf
Data publikacji:
2018
Wydawca:
Fundacja Ekonomistów Środowiska i Zasobów Naturalnych
Tematy:
water supply
risk
risk matrix
zaopatrzenie w wodę
ryzyko
macierz ryzyka
Opis:
The new regulation concerning the quality of drinking water offers a number of delegations on the waterworks inform users about the quality of tap water. The study analysis on the public risk health should be prepared. In the paper the analysis and assessment method of the population and property related to failure occurrence of collective water supply systems is presented. Four categories of factors having impact on the multiplicative risk: purity category or probability of danger occurrence, material damage, loss of population health and security were adopted. On this basis four-parametric risk matrix was developed. In the study also examples of application methods were presented. The method can provide a planning tool in crisis management at the local government level.
Źródło:
Ekonomia i Środowisko; 2018, 2; 8-17
0867-8898
Pojawia się w:
Ekonomia i Środowisko
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Precession Electron Diffraction Studies of $Sr_x Ba_{1-x} Nb_2 O_6$ and $Ca_x Ba_{1-x} Nb_2 O_6$ Single Crystals
Autorzy:
Wspaniała-Rak, J.
Zubko, M.
Stróż, D.
Rak, J.
Dec, J.
Powiązania:
https://bibliotekanauki.pl/articles/1398360.pdf
Data publikacji:
2016-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.50.Ah
68.37.Lp
68.55.Nq
Opis:
Crystal structures of two single crystals $Sr_x Ba_{1-x} Nb_2 O_6$ and $Ca_x Ba_{1-x} Nb_2 O_6$ have been reinvestigated using automated electron diffraction tomography method with beam precession. 3D reciprocal space has been reconstructed based on recorded tilt series. For both samples the crystal structure was refined and the tetragonal symmetry with space group P4bm was confirmed. The three dimensional reciprocal space allowed to observe and to study satellite reflections in both materials.
Źródło:
Acta Physica Polonica A; 2016, 130, 4; 830-832
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Martensite reorientation after thermal cycling in NiTiCu shape memory alloys studied by EBSD technique
Autorzy:
Rak, J.
Goryczka, T.
Ochin, P.
Powiązania:
https://bibliotekanauki.pl/articles/1153063.pdf
Data publikacji:
2016-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.20.fg
68.37.Hk
Opis:
The Ni₂₅Ti₅₀Cu₂₅ shape memory alloy exhibits one-step martensitic transformation. Transformation occurs between the B2 parent phase and the B19 orthorhombic martensite. The course of the martensitic transformation was in situ studied in the alloy with use of electron backscatter diffraction. During heating, reverse martensitic transformation occurs from the B19 orthorhombic martensite to the B2 parent phase. On cooling, from the parent phase the B19 martensite is formed. Obtained results proved that the B19 martensitic plates forms the variants indexed as 1, 3, and 5. Thermal cycling does not change the crystallographic correlation between the parent phase and the martensite. However, after cycling, different rearrangement of the martensitic plates can be received. In consequence, characteristic temperatures of the martensitic transformation are shifted.
Źródło:
Acta Physica Polonica A; 2016, 130, 4; 1075-1078
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of risk and failure scenarios in water supply system
Autorzy:
Boryczko, K.
Rak, J.
Tchórzewska-Cieślak, B.
Powiązania:
https://bibliotekanauki.pl/articles/2069508.pdf
Data publikacji:
2014
Wydawca:
Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:
fault tree analysis
matrix methods
risk analysis
water supply system
Opis:
Water supply system is complicated technical system which belongs to underground urban infrastructure. Its accurate functioning determines everyday live stability of citizens. Risk analysis is a key phase of the process of water supply safety management. The aim of this paper is to present new propose of methods for risk of the first type (associated with quantity of supplied water) and the risk of the second type (associated with quality of supplied water) analyses in water supply system. The paper contains the description of matrix methods for risk analyses and methods describing cause-and-effect relationship of failure events (fault tree analysis).
Źródło:
Journal of Polish Safety and Reliability Association; 2014, 5, 2; 11--18
2084-5316
Pojawia się w:
Journal of Polish Safety and Reliability Association
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
NetBaltic system – heterogeneous wireless network for maritime communications
Autorzy:
Hoeft, M.
Gierłowski, K.
Rak, J.
Woźniak, J.
Powiązania:
https://bibliotekanauki.pl/articles/260004.pdf
Data publikacji:
2018
Wydawca:
Politechnika Gdańska. Wydział Inżynierii Mechanicznej i Okrętownictwa
Tematy:
maritime communication systems
heterogeneous maritime network
mobility management
maritime mesh networks
delaytolerant networks
Opis:
In case of maritime communications, we observe a growing interest in deployment of multitask satellite-based solutions and development of new maritime-specific systems intended for improvements in safety of e-navigation. Analysis of different types of currently used maritime communication systems leads, however, to a conclusion that neither global and still very expensive satellite systems nor cheaper, but short-ranged transmission technologies can, on their own, fully meet the today’s expectations and quality requirements formulated for broadband maritime systems. This lack of reliable solutions, offering high throughput and ubiquitous availability of coverage to a wide audience at a relatively low price is one of the main barriers in a widespread implementation of e-navigation initiatives. This issue is addressed in the netBaltic project with the objective to design, deploy and validate in a real maritime environment a non-satellite wireless communication system enabling ship-to-ship and ship-to-shore information exchange via a multi-hop network composed of onshore base stations, maritime vessels and other transit elements such as buoys. In this paper, the idea of a heterogeneous wireless maritime system is presented. Details of the proposed netBaltic node architecture are described highlighting the solutions introduced in the project as a response to specific maritime communication requirements. Numerical results of communication area coverage are presented for four different scenarios utilizing different wireless transmission technologies. In particular, they indicate that when using appropriate wireless communication solutions, the number of vessels being able to connect to Internet is significantly increased as compared to traditional wireless systems (capable of one-hop communication) from 14% for short-range transmission technologies up to as high as 127% in case when relatively long-range transmission technologies are employed within the system.
Źródło:
Polish Maritime Research; 2018, 2; 14-26
1233-2585
Pojawia się w:
Polish Maritime Research
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Risk analysis of water supply interruptions in collective water supply systems
Autorzy:
Tchórzewska-Cieślak, B.
Rak, J. R.
Piegdoń, I.
Powiązania:
https://bibliotekanauki.pl/articles/2069330.pdf
Data publikacji:
2012
Wydawca:
Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:
water supply
availability
risk management
value of water scarcity
water production subsystem
Opis:
The subject and main purpose of this study is to present the method of risk analysis and assessment of the lack of water supply to the collective water supply system (CWSS). Presented method using the expected value of water scarcity. The analysis was based on all possible states of the operation of water production subsystem. The article contains calculation example of analysis for the exemplary CWSS with regard to absolute risk, equal to the expected value of water scarcity and the relative risk referred to the nominal value of the water demand. In the example attached special importance to the criteria levels of the relative risk of lack of water supply. Presented method is a new concept which allows to make comprehensive analysis of reliability, safety and operation of the collective water supply system.
Źródło:
Journal of Polish Safety and Reliability Association; 2012, 3, 2; 201--208
2084-5316
Pojawia się w:
Journal of Polish Safety and Reliability Association
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Failure risk analysis in the water supply sector management
Autorzy:
Tchórzewska-Cieślak, B.
Rak, J. R.
Pietrucha, K.
Powiązania:
https://bibliotekanauki.pl/articles/2069627.pdf
Data publikacji:
2011
Wydawca:
Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:
water supply
risk management
safety
critical infrastructure
Opis:
The subject and main purpose of this study is to develop risk analytic model for the design and operation of water supply sector. A water supply system belongs to the critical infrastructure of cities, and it should be a priority task for waterworks and even for the local authorities to ensure the suitable level of its safety. A water supply systems (WSS) ought to be high reliable continuous operating system. Failure factors in WSS should be identified and prioritized, for example, the causing factors in the most frequent failures in waterpipe network. Drinking water supply utilities are responsible for providing a safe and reliable supply of potable water to their customers. Risk priority helps asset manager to target and refine maintenance plans, capital expenditure plans, investigative activities, and deal with potential failure before it occurs. In this paper, we present a review of classic risk analyses, risk management and new methodology for water supply networks management. This paper presents a framework for the analysis of performance risk in water supply that can be applied to the entire system or to individual subsystems. It is expecting that the methodology for the water supply performance risk analysis would provide the city leadership for decision making support.
Źródło:
Journal of Polish Safety and Reliability Association; 2011, 2, 1; 185--196
2084-5316
Pojawia się w:
Journal of Polish Safety and Reliability Association
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Integrated multimotor electrical dc drive for metallurgical rolling table
Autorzy:
Gała, M.
Jąderko, A.
Rak, J.
Jagiełła, K.
Powiązania:
https://bibliotekanauki.pl/articles/386472.pdf
Data publikacji:
2015
Wydawca:
Politechnika Białostocka. Oficyna Wydawnicza Politechniki Białostockiej
Tematy:
FEX excitation system
DC drive system
rolling table
DriveWindow software
system napędowy
DSL
sterowniki PLC
Opis:
A drive system of a section of a metallurgical rolling table consisting of six dc motors, 2220 amperes of total current, fed from a single ABB reversible thyristor converter has been described in this paper. Autonomous excitation circuits of the motors are fed from independent thyristor converters working in the so called MULTIFEX system linked with a supervisory high power converter. There are presented schemes of the DSL communication realized by FEX excitation cards of the motors using the SDSC card of the DCS-800-S02 converter and logic control system based on a PLC controller. The parameterization of the DCS-800 converter and the DCF 803 excitation systems was conducted using the DriveWindow software tool. Significant waveforms of voltages, currents and the estimated motor velocity are described and presented for the idle run as well as during transporting sheets discharged from a pusher furnace.
Źródło:
Acta Mechanica et Automatica; 2015, 9, 2; 93-98
1898-4088
2300-5319
Pojawia się w:
Acta Mechanica et Automatica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Safety analysis of water supply systems including protection barriers
Autorzy:
Pietrucha-Urbanik, K.
Rak, J. R.
Tchórzewska-Cieślak, B.
Powiązania:
https://bibliotekanauki.pl/articles/2069151.pdf
Data publikacji:
2013
Wydawca:
Uniwersytet Morski w Gdyni. Polskie Towarzystwo Bezpieczeństwa i Niezawodności
Tematy:
water supply system
protection barriers
event tree
Opis:
Water quality control from the perspective of water supply system users’ safety contributed to create drinking water production and quality control procedures. Contemporary risk hazard analysis should be performed on the stage of production, distribution and storage of tap water. Sequences of undesirable events are considered in the so-called waterworks chain series. This leads to critical control points and gives the ability to provide current control over the processes in the collective water supply system, as well as of their combinations and mutual interactions. Methodology of water consumers protection against incidental pollutions was shown. Algorithm concerning identification of critical control points – CCP was developed .The rules of safety related system into drinking water production have been shown. Also risk assessment using the tree event method was presented.
Źródło:
Journal of Polish Safety and Reliability Association; 2013, 4, 2; 241--248
2084-5316
Pojawia się w:
Journal of Polish Safety and Reliability Association
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Influence of Passivation Type on Corrosion Resistance of Ti15Mo Alloy in Simulated Body Fluids
Wpływ rodzaju pasywacji powierzchni stopu Ti15Mo na jego odporność korozyjną w środowisku płynów ustrojowych
Autorzy:
Szklarska, M.
Dercz, G.
Rak, J.
Łosiewicz, B.
Simka, W.
Powiązania:
https://bibliotekanauki.pl/articles/353709.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
biomaterial
electrochemical impedance spectroscopy
corrosion resistance
passivation
titanium alloys
biomateriały
elektrochemiczna spektroskopia impedancyjna
odporność na korozję
pasywacja
stopy tytanu
Opis:
This work reports on determination of the influence of passivation type of Ti15wt.%Mo implant alloy surface on its corrosion resistance in simulated body fluids. The alloy under investigation was subjected to natural self-passivation in air, and forced passivation by autoclaving in steam, boiling in 30 % solution of H2O2, and electrochemical passivation in 0.9 % NaCl solution. Resistance of the passivated Ti15Mo alloy to pitting corrosion was studied at 37ºC in 0.9 % NaCl solution using open circuit potential method, anodic polarization curves, and electrochemical impedance spectroscopy (EIS). Comparative estimation of the determined parameters of corrosion resistance revealed that the obtained passive layers improve anticorrosive properties of the tested alloy. Surface of the alloy subjected to passivation in steam autoclave reveals the highest protection against pitting corrosion. Anodic potentiodynamic curves showed that the Ti15Mo alloy after different passivation types of the surface is characterized by a lack of susceptibility to pitting corrosion up to potential of 9 V. Based on the EIS investigations, the thickness of the formed oxide layers (TiO2, anatase) was determined to be in the range from 2.0 to 7.8 nm in dependence on the applied type of passivation. It was ascertained that electrochemical properties of the Ti15Mo alloy and possibility of its surface passivation using simple methods, make it an attractive material for use in biomedicine for long-term implants.
Praca dotyczy określenia wpływu rodzaju pasywacji powierzchni stopu Ti15%wag.Mo na jego odporność korozyjną w środowisku płynów ustrojowych. Badany stop poddano naturalnej samopasywacji w powietrzu oraz wymuszonej pasywacji w autoklawie parowym, w gotującym się 30 % roztworze H2O2 oraz elektrochemicznej pasywacji w 0,9 % roztworze NaCl. Odporność pasywowanego stopu Ti15Mo na korozję wżerową badano w temperaturze 37°C w roztworze 0,9 % NaCl metodą potencjału obwodu otwartego, krzywych polaryzacji anodowej oraz elektrochemicznej spektroskopii impedancyjnej (ESI). Ocena porównawcza wyznaczonych parametrów odporności korozyjnej wykazała, że wytworzone warstwy pasywne poprawiają właściwości antykorozyjne badanego stopu. Powierzchnia stopu poddana pasywacji w autoklawie parowym wykazuje najwyższą ochronę przed korozją wżerową. Anodowe krzywe potencjodynamiczne ujawniły, że stop Ti15Mo poddany różnym sposobom pasywacji powierzchni wykazuje brak podatności na korozję wżerową aż do potencjału wynoszącego 9 V. W oparciu o badania ESI wyznaczona została grubość otrzymanych warstw tlenkowych (TiO2, anataz), która w zależności od zastosowanego sposobu pasywacji mieściła się w zakresie od 2,0 do 7,8 nm. Stwierdzono, że właściwości elektrochemiczne stopu Ti15Mo oraz możliwość pasywowania jego powierzchni prostymi metodami, czynią go atrakcyjnym materiałem do zastosowań w biomedycynie na implanty długoterminowe.
Źródło:
Archives of Metallurgy and Materials; 2015, 60, 4; 2687-2694
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase analysis of NiTi shape memory wires and computer simulations of the superelastic effect
Autorzy:
Młocek, B.
Lekston, Z.
Zubko, M.
Rak, J.
Stróż, K.
Powiązania:
https://bibliotekanauki.pl/articles/1058069.pdf
Data publikacji:
2016-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
02.70.-c
62.20.F-
81.70.-q
Opis:
Shape memory alloys belong to the group of intelligent materials due to their exceptional properties related to reversible martensitic transformation. They show both superelasticity and shape memory effects. The modelling of the superelastic phenomena occurring in NiTi alloys is important due to its application in the further development of materials for dedicated applications. A computer simulation of static tensile test was carried out using the finite element method for NiTi wire and obtained results were compared with experimental curve. For the determination of phase composition at ambient temperature and courses of phase transitions during cooling and heating the X-ray powder diffraction and differential scanning calorimetry methods were used. X-ray diffraction phase analysis exhibited that the studied wire at room temperature has B2 - parent phase structure. Additionally, differential scanning calorimetry measurements showed that the phase transformations during cooling and heating occur in a temperature range of about -20 to +30°C.
Źródło:
Acta Physica Polonica A; 2016, 130, 4; 1063-1065
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of creep on crystallographic orientation in single crystal superalloy
Autorzy:
Albrecht, R.
Rak, J.
Bogdanowicz, W.
Gancarczyk, K.
Sieniawski, J.
Kubiak, K.
Lelątko, J.
Powiązania:
https://bibliotekanauki.pl/articles/1075665.pdf
Data publikacji:
2016-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.72.Ff
81.10.Aj
61.72.Hh
Opis:
The creep-rupture tests were performed on a single crystal rods made of CMSX-4 superalloy obtained at withdrawal rates of 3 and 5 mm/min. After the rupture the microstructure and fracture surface were examined and correlated with X-ray crystal rotation measurements by the Ω-scan method. The conclusions about the crystal lattice rotation during creep test were provided.
Źródło:
Acta Physica Polonica A; 2016, 130, 4; 1094-1096
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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