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Tytuł:
Formation of Transition Phases on Interface between Monocrystalline Fe and Cu Due to Mutual Solid-State Diffusion
Autorzy:
Perek-Nowak, M.
Boczkal, G.
Powiązania:
https://bibliotekanauki.pl/articles/351905.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
copper single crystals
iron single crystal
transition phase
solid-state diffusion
Opis:
Interdiffusion between Fe (Armco) and Cu single crystals of similar orientation (around [110]) annealed at temperatures of 873 and 973K in air for 0.5 up to 4 h is studied. Formation of three phases different in their chemical composition has been observed: 1) oxide layer on Cu border (porous), 2) a layer rich in copper, iron and oxygen, 3) a layer of iron and oxygen with only small addition of Cu. All reactions of interface formation occurred in solid state. It was noted that oxygen plays an important role in development of new phases. Strong Kirkendall effect is observed due to large difference in diffusion coefficients of copper atoms to iron, DCu→Fe=300exp(-67800/RT) and iron atoms to copper DCu→Fe=0.091exp(-46140/RT).
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 2A; 581-586
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Sn and Pb Ions Substitutions on Dielectric Properties of Barium Titanate
Autorzy:
Bąk, W.
Kajtoch, C.
Ptaszek, S.
Lisińska-Czekaj, A.
Czekaj, D.
Ziętek, D.
Glos, T.
Garbarz-Glos, B.
Powiązania:
https://bibliotekanauki.pl/articles/352509.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
barium titanate ceramics
dielectric properties
phase transition
Opis:
The results of the microstructural and dielectric measurements of (Ba1-xPbx)(Ti1-xSnx)O3 (BPTSx) (x = 0, 0.05, 0.10, 0.30) polycrystalline samples are presented. The samples were obtained by means of a high temperature synthesis and their expected stoichiometry was confirmed by energy dispersive spectroscopy (EDS) measurements. The dielectric properties of BPTSx were studied with the use of broadband dielectric spectroscopy. The measurements over a wide range of temperature (from 140 K to 600 K) and frequency (from 0.1 Hz to 10 MHz) were performed. The experimental results indicate an influence of Pb ions in a sublattice A and Sn ions in a sublattice B substitution on paraelectric - ferroelectric phase transition parameters. Diffused phase transitions from a paraelectric to ferroelectric state (for x = 0.10 and x = 0.30) were observed. From the electric modulus measurements in the frequency domain the relaxation times and the activation energy were determined.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 2A; 905-908
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Microstructural Evolution in HMX Based Plastic-bonded Explosive During Heating and Cooling Process: an in situ Small-angle Scattering Study
Autorzy:
Yan, G.
Tian, Q.
Liu, J.
Fan, Z.
Sun, G.
Zhang, C.
Wang, Y.
Chen, B.
Gong, J.
Zhou, X.
Yang, Z.
Nie, F.
Li, J.
Li, X.
Powiązania:
https://bibliotekanauki.pl/articles/358618.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
SANS
SAXS
HMX-PBX
thermal damages
phase transition
Opis:
The thermal damage in octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) based plastic-bonded explosive (PBX) was investigated using in situ small-angle neutron and X-ray scattering techniques. The microstructural evolution was quantitatively characterized by the model fitting parameters of total interfacial surface area (Sv) and void volume distribution. The Sv of HMX-PBX decreased markedly above 100 °C, indicating the movement of binder into the voids. After subsequent cooling to room temperature, the scattering intensity increased significantly with increasing storage time, and a new population of voids with average diameter of 20 nm was observed, accompanied by the gradual phase transition of HMX from δ- to β-phase. The experimental results implied that serious damage within the HMX-PBX was developed during storage after heating.
Źródło:
Central European Journal of Energetic Materials; 2016, 13, 4; 916-926
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Transition and Plasticity Enhancement of Ti-Cu-Based Bulk Metallic Glasses
Autorzy:
Wang, L.
Wang, X.
Zhang, G.
Sun, X.
Powiązania:
https://bibliotekanauki.pl/articles/356824.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
bulk metallic glasses
phase transition
annealing
stability
plasticity
Opis:
In this paper, we report the complex crystallization kinetics of phase transition happening in Ti-Cu-based bulk metallic glasses (BMGs), which play significant roles in the glass formation with respect to their low reduced glass transition temperatures, Trg. The first exothermic event just occurs when annealing the BMG samples in the supercooled liquid region, leading to the Avrami exponent deviating from conventional modes affected by the residual amorphous phase. For Ti43Cu43Ni7Zr7 BMG, the plasticity can be improved by pre-annealing at a sub-Tg temperature of 623K (≈50K below Tg) for 0.5 hour, however, deteriorated by 1 hour annealing, which could be related to the change in stability of this BMG against crystallization with different pre-annealing times.
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 1; 387-391
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Badanie rozwoju i zaniku wrzenia czynnika chłodniczego w kanale
Investigations of development and decay of boiling of the refrigerant in a channel
Autorzy:
Bohdal, T.
Powiązania:
https://bibliotekanauki.pl/articles/158407.pdf
Data publikacji:
2010
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
chłodnictwo
przemiany fazowe
niestabilności
refrigeration
phase transition
instabilities
Opis:
Przeprowadzono badania eksperymentalne rozwoju i zaniku wrzenia pęcherzykowego proekologicznych czynników chłodniczych w kanale rurowym. Procesom tym towarzyszy zjawisko zerowego kryzysu wrzenia związane z histerezą aktywizacji zarodków. Potwierdzono, że rozwój i zanik wrzenia wykazuje własności falowe. Rozwój wrzenia następuje w postaci tzw. frontu wrzenia, który przemieszcza się przeciwnie do kierunku przepływu z prędkością zależną od przegrzania cieczy przy ogrzewanej ściance. Analogicznie zanik wrzenia sukcesywnie postępuje zgodnie z kierunkiem przepływu czynnika. Badania potwierdziły występowanie histerezy rozwoju i zaniku wrzenia pęcherzykowego w kanale.
Experimental investigations of development and decay of bubbly boiling of environment-friendly refrigerants in a tubular channel were performed. These processes are accompanied by the zero boiling crisis phenomenon connected with the nuclei activation hysteresis. It was confirmed that the development and decay of boiling have wave properties. The development of boiling occurs in the form of the so-called boiling front which shifts in the direction opposite to the flow direction with the speed dependent on the wall superheat. The decay of boiling progresses successively in compliance with the refrigerant flow direction. The tests confirmed the occurrence of development and decay hysteresis of bubbly boiling in the channel. In the description including the wave effect, there was taken into account the pressure change impulse vp and boiling front vt translocation velocity. These velocities depend on the refrigerant spore filling ? in a channel . Besides, bubble boiling in flow has a very important employment aspect. Such phenomena occur not only in evaporators of cooling devices, but also in other energy systems. Under dynamic conditions some changes of parameters can cause negative exploitation qualities characterised by instability of machines and motors.
Źródło:
Pomiary Automatyka Kontrola; 2010, R. 56, nr 4, 4; 337-343
0032-4140
Pojawia się w:
Pomiary Automatyka Kontrola
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Molecular dynamics study of temperature-induced structural changes in YBa2Cu3O7 crystal
Autorzy:
Bośko, J.
Sadowski, W.
Powiązania:
https://bibliotekanauki.pl/articles/1954521.pdf
Data publikacji:
1999
Wydawca:
Politechnika Gdańska
Tematy:
MD simulations
structure
phase transition
oxygen diffusion
trajectory
Opis:
The structure of YBa2Cu3O7 crystal has been studied with the aid of molecular-dynamics (MD) technique. A two-body model potentials proposed by Zhang and Catlow have been used in MD simulations performed in wide range of temperature. The temperature-induced orthorhombic-to-tetragonal phase transition is observed. The distruction of the arrangement of atoms in the CuO chains due to diffusion of oxygen atoms is observed. The diffusion coefficients are calculated, and their variation as a function of temperature is analysed. The activation energy is estimated.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 1999, 3, 3; 293-302
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Irradiation of austenitic steel 10Cr12Mn14Ni4AlMo and titanium alloy Ti-Al-V by pulsed streams of fast nitrogen ions and plasma in a dense plasma focus
Autorzy:
Gribkov, V. A.
Pimenov, V. N.
Roschupkin, V. V.
Maslyaev, S. A.
Demina, E. V.
Lyakhovitsky, M. M.
Dubrovsky, A. V.
Sasinovskaya, I. P.
Powiązania:
https://bibliotekanauki.pl/articles/971548.pdf
Data publikacji:
2012
Wydawca:
Instytut Chemii i Techniki Jądrowej
Tematy:
radiation
damage
phase transition
nanohardness
dense plasma focus (DPF)
Opis:
Austenitic steel 10Cr12Mn14Ni4AlMo and Ti-4Al-3V alloy were irradiated with nanosecond pulsed nitrogen ion and plasma streams in plasma focus devices. The two different modes of the treatment were applied: high power density (greater-than or equal to 10 8 W/cm2) irradiation with melting of the surface layer and irradiation with power density similar to 10 7 W/cm2 below the melting threshold. Structure and phase changes as well as the mechanisms of modification and hardening of the surface layers of the steel and titanium alloy upon applied irradiation are discussed.
Źródło:
Nukleonika; 2012, 57, 2; 291-295
0029-5922
1508-5791
Pojawia się w:
Nukleonika
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of phase transition in Bi3TiNbO9-BaBi2Nb2O9 ceramics
Autorzy:
Adamczyk, M.
Kusz, J.
Hofmeister, W.
Zubko, M.
Kozielski, L.
Pilch, M.
Bochenek, D.
Wodecka-Duś, B.
Powiązania:
https://bibliotekanauki.pl/articles/353210.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
dielectric properties
X-ray methods
grain size
phase transition
ceramics
Opis:
The subject of the paper is lead free bismuth layer structure oxides (1-x)Bi3TiNbO9-xBaBi2N2O9(x=0; 1; 2; 3 mol). The influence of Bi3TiNbO9/BaBi2Nb2O9 ratio on dielectric and structural properties was studied in a wide range of temperatures. Change in the ratio causes a decrease in the maximum value of dielectric permittivity and shifts the temperature of ε`max to low values, leading to linear decreasing of average grain size and linear increasing of ceramics density. These results indicate an augment of the packing degree and the participation of pores are significantly decreased with the increase of BaBi2Nb2O9compound intake. Moreover, for 0.7Bi3TiNbO9-0.3BaBi2Nb2O9 ceramics the dielectric phase transition is broadened and the properties characteristic for the ferroelectric relaxor appear.
Źródło:
Archives of Metallurgy and Materials; 2016, 61, 3; 1503-1510
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Selected magnesium compounds as possible inhibitors of ammonium nitrate decomposition
Autorzy:
Hoffmann, Józef
Kaniewski, Maciej
Nieweś, Dominik
Hoffmann, Krystyna
Powiązania:
https://bibliotekanauki.pl/articles/780057.pdf
Data publikacji:
2020
Wydawca:
Zachodniopomorski Uniwersytet Technologiczny w Szczecinie. Wydawnictwo Uczelniane ZUT w Szczecinie
Tematy:
ammonium nitrate
thermal analysis
magnesium compounds
exothermic decomposition
phase transition
Opis:
Ammonium nitrate (AN) is considered to be a very hazardous and difficult to handle component of mineral fertilizers. Differential thermal analysis coupled with thermogravimetry and mass spectrometry was used to determine the possible inhibiting effect of selected magnesium compounds on thermal decomposition of AN. Each additive was mixed with AN to create samples with AN:magnesium compound mass ratios of 4:1, 9:1 and 49:1. Most of analyzed compounds enhanced thermal stability of ammonium nitrate, increasing the temperature of the beginning of exothermic decomposition and decreasing the amount of generated heat. Magnesium chloride hexahydrate was determined to accelerate the decomposition of AN while magnesium sulphate, sulphate heptahydrate, nitrate hexahydrate together with magnesite and dolomite minerals were defi ned as inhibiting agents.
Źródło:
Polish Journal of Chemical Technology; 2020, 22, 2; 1-8
1509-8117
1899-4741
Pojawia się w:
Polish Journal of Chemical Technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Stability of Ammonium Nitrate with Organic Potassium Salts
Autorzy:
Xu, Z.-X.
Fu, X.-Q.
Wang, Q.
Powiązania:
https://bibliotekanauki.pl/articles/358264.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
ammonium nitrate(V)
phase transition
organic compounds
differential scanning calorimetry
Opis:
A study has been undertaken on the effect of additives on the phase transition of ammonium nitrate(V) (AN). Results obtained using Differential Scanning Calorimetry (DSC) showed that organic compounds and potassium salts of organic compounds have an effect on the phase transition behavior of AN. The samples were further analyzed using infrared (IR) and powder X-ray diffraction (XRD). The mechanism of phase stabilization of AN by compounds of this kind was examined. The present study showed that the influence of additives on the phase transition of AN occurs through the polar groups that are involved in intermolecular interactions of orbital and electrostatic types that form new hydrogen bonds. AN exists in only one phase in the temperature range from 30 °C to +100 °C, when a potassium salt of organic compounds was added. However, with organic compounds, the III→II phase transition was changed. IR and XRD of composites are characterized by new intermolecular interactions. Compacted samples of AN containing potassium salts of organic compounds exhibited better stability than AN containing organic compounds to multiple cyclic changes within a temperature range. This we named ‘freezing and thawing analysis’. Additives have two functions on the AN phase transition. First, solid solutions of AN mixture were formed for K+ replacement of NH4+. Second, hydrogen bonds formed, which caused AN and salts of organic compounds to interact intimately.
Źródło:
Central European Journal of Energetic Materials; 2016, 13, 3; 736-754
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the Thermal Behaviour of CL-20, Potassium Perchlorate, Lithium Perchlorate and Their Admixtures by DSC and TG
Autorzy:
Zhang, J.-J.
Guo, X.-J.
Jiao, Q.-J.
Zhang, H.-L.
Li, H.
Powiązania:
https://bibliotekanauki.pl/articles/358770.pdf
Data publikacji:
2018
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
CL-20
potassium perchlorate
lithium perchlorate
thermal stability
phase transition
Opis:
The thermal decomposition characteristics of CL-20, potassium perchlorate (KP), lithium perchlorate (LP), a CL-20/KP mixture, and a CL-20/LP mixture were studied using thermogravimetry-differential scanning calorimetry (TG-DSC). The DSC curves for KP exhibited three endothermic peaks and one exothermic peak. The first two endothermic peaks correspond to the rhombic-cubic transition and the fusion of KP, respectively, the third indicates the fusion of KCl, while the exothermic peak is attributed to the decomposition of KP. The DSC curves obtained from LP showed four endothermic peaks and one exothermic peak. The first two endothermic peaks indicate the loss of adsorbed water and water of crystallization, while the third and fourth are associated with the fusion of LP and LiCl, respectively; the exothermic peak is due to the decomposition of LP. The presence of KP had little effect on the thermal decomposition of CL-20 while the addition of LP increased the temperature at which CL-20 exhibits an exothermic peak. In addition, the thermal decomposition of LP appeared to be catalyzed by the presence of CL-20.
Źródło:
Central European Journal of Energetic Materials; 2018, 15, 1; 115-130
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Curie temperatures for the Ising model on Archimedean lattices
Autorzy:
Malarz, K.
Zborek, M.
Wróbel, B.
Powiązania:
https://bibliotekanauki.pl/articles/1964143.pdf
Data publikacji:
2005
Wydawca:
Politechnika Gdańska
Tematy:
computer modelling and simulation
Ising model
phase transition
critical parameter
Opis:
Critical temperatures for the ferro-paramagnetic transition in the Ising model are evaluated for five Archimedean lattices, basing on Monte Carlo simulations. The obtained Curie temperatures are 1.25, 1.40, 1.45, 2.15 and 2.80 [J/kB] for (3,12 do2), (4,6,12), (4,8 do 2), (3,4,6,4) and (3 do 4,6) lattices, respectively.
Źródło:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2005, 9, 4; 475-480
1428-6394
Pojawia się w:
TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermally Induced Polymorphic Transformation of Hexanitrohexaazaisowurtzitane (HNIW) Investigated by in-situ X-ray Powder Diffraction
Autorzy:
Liu, Y.
Li, S.
Wang, Z.
Xu, J.
Sun, J.
Huang, H.
Powiązania:
https://bibliotekanauki.pl/articles/358065.pdf
Data publikacji:
2016
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
HNIW
polymorphism
in situ X-ray diffraction
phase transition
heat stimulation
Opis:
The ε→γ phase transition of HNIW induced by heat was investigated with in situ X-ray powder diffraction (PXRD). The effects of purity, particle size, insensitive additives and the time of isothermal heat treatment on the phase transition were evaluated. It was found that the phase transition is irreversible with changes in temperature, and the two phases can coexist in a certain temperature range. Moreover, the initial phase transition temperature increases with increasing purity and decreasing particle size of HNIW, and thus with the approximate crystal density. The addition of graphite and paraffin wax to HNIW as insensitive additives leads to a decrease in the initial phase transition temperature, but the addition of TATB does not affect the initial phase transition temperature. Thus, TATB is a suitable insensitive additive. Moreover, at the critical temperature, the isothermal time determined the efficiency of the ε- to γ-phase transition. This work lays the foundations for the choice of molding technologies, performance test methods, ammunition storage options, as well as the manufacture of HNIW-based explosive formulations.
Źródło:
Central European Journal of Energetic Materials; 2016, 13, 4; 1023-1037
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analiza niestabilności przemian fazowych czynników energetycznych. Część I- Ocena stanu wiedzy
Analysis of instability in phase transitions of energy media. Part I assessment of knowledge
Autorzy:
Bohdal, T.
Powiązania:
https://bibliotekanauki.pl/articles/1819662.pdf
Data publikacji:
2010
Wydawca:
Politechnika Koszalińska. Wydawnictwo Uczelniane
Tematy:
czynnik energetyczny
przemiana fazowa
nośniki energii
energy factor
phase transition
energy carriers
Opis:
W opracowaniu ograniczono zakres analizy do dwóch charakterystycznych przemian fazowych, to znaczy wrzenia i skraplania. Brak pełnej odwracalności między tymi przemianami nie pozwala na deterministyczny sposób ich analizy, bowiem ich realizacji towarzyszą, niekiedy jakościowo różne zjawiska. Bez względu na to, czy przemiana fazowa zachodzi w objętości, czy też w przepływie, występowanie stanów niestabilnych tłumaczy się powstawaniem warunków nierównowagi termodynamicznej podczas ich realizacji. Wspólna przyczyna wywołania niestabilności skutkuje bardzo wieloma ich odmianami. Według obecnego stanu wiedzy klasyfikacja typów niestabilności jest bardzo utrudniona, z uwagi na znaczne rozproszenie źródeł bibliograficznych oraz stosowaną terminologię. Podkreślić należy, że zdecydowana większość publikacji w literaturze dotyczy prezentacji wyników badań eksperymentalnych, natomiast od kilku lat obserwuje się systematyczny wzrost liczby publikacji zawierających analizy teoretyczne niestabilności przemian fazowych. Istnieje jednak wiele obszarów, które wymagają dalszych badań.
A principle of operation of some machines and electrical equipment consists in making use of the phase transition of energy media in a thermodynamic cycle. Under the notion of an energy medium we understand both the energy carrier and also the thermodynamic factor being subject to the transitions and taking part in the conversion of energy, being directly or indirectly involved in it. Water, refrigerants, water solutions of salt, etc are rated among energy media. The fact that the phase transitions of energy media occurring in evaporators and condensers of machines and equipment are very 'sensitive' to all the instabilities, both external and internal in character, appearing in the course of operational use could be considered as well-substantiated. In general, the instabilities in a two-phase flow could be divided into two categories. The flow is considered as static stable if the source of instabilities is inseparably tied up with parameters of the steady-state system. Due to the fact, that the instability follows from a change in value of the steady-state system parameters one can expect that it is possible to predict the onset of the instability merely knowing this steady state. The static instability mostly leads to the other working point of this system in a steady state or the periodic oscillations in its behaviour. As an example of static instabilities the instability of the first boiling crisis or a so-called Leddinegg instability could be mentioned. The instability of the first boiling crisis takes place in case of changing the heat-exchange mechanism during the process of boiling in volume. When the heat flux on the heated surface reaches the critical value the bubble boiling is replaced by the film boiling. If the thermal or hydrodynamic reactions, giving the distinct inertial effects, are the main reason for the system instabilities, then the flow is unstable, dependent on so-called dynamic instabilities. Such the instabilities in flow through the two-phase medium of a fluid-gas type could be transferred by means of two mechanisms, i.e. the acoustic waves (pressure instabilities) and the waves of mass flux density change (as an effect of the filling ratio fluctuations). These phenomena are wavy in character, but the velocities of wave propagation are very different. The acoustic waves are marked by high frequencies, whereas the wave oscillations of mass flux density change usually have much lower frequency. The acoustic instabilities result from the pressure-wave propagation in a two-phase flow. The acoustic oscillations may occur during the subcooled boiling and at the developed boiling in flow providing the critical heat flux was reached and the system was converted into the film boiling. According to Ber-gles, the acoustic oscillations may affect the course of flow. An amplitude of the acoustic pressure oscillations may reach the high value, compared the average value of the fluctuation frequency transition in two-phase media. The frequency of oscillations of this type recorded during the experimental investigations was within the scope 10 -10 000 Hz. The wave of the mass flux density change velocity is relatively low, due to the time required for the fluid particle to flow through a coil pipe. Waves of this type are observed mostly in the course of boiling in flow, when a coil pipe is supplied with the fluid heated below the temperature of saturation (subcooled boiling). These oscillations follow directly from the relation between the process of boiling and the properties of a two-phase flow. An instantaneous drop in a flow rate at the intake results in an increase of the specific enthalpy in this region. The higher enthalpy at a part of a subcooled flow leads to a local rise in temperature of the medium. It reduces the value of fluid underheating to the saturation temperature and shifts the initial point of boiling inversely to a flow of the medium. From the onset of boiling in flow, a local filling ratio and a coefficient of vapour dryness in a coil pipe were increasing. A local increase in the vapour dryness and the filling ratio led to the instability in a thickness of a thin film of fluid on a coil pipe wall. It can produce a change in the flow structure from a bubble an annular flow, which consequently causes the flow to be re-accelerated. There is an increase in a local gradient of pressure leading to the further drop in a total pressure during the two-phase flow in a coil pipe. Small fluctuations in a flow rate could be intensified until the specific amplitude of the wave of the mass flux density change was obtained. It has been confirmed by experimental investigations, which reveal the characteristic oscillation features of the wave of the mass flux density change. They pointed out that the oscillations of the wave of the mass flux density change are strongly dependent of changes in a heat flux density, a degree of cross-section reduction at the intake and the outlet of the medium in a coil pipe, a single- and two-phase frictional pressure drop in a coil pipe, super-cooling, a flow rate of the medium and changes in the system pressure.
Źródło:
Rocznik Ochrona Środowiska; 2010, Tom 12; 61-93
1506-218X
Pojawia się w:
Rocznik Ochrona Środowiska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Canonical distributions and phase transitions
Autorzy:
Athreya, K
Smith, J
Powiązania:
https://bibliotekanauki.pl/articles/729916.pdf
Data publikacji:
2000
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
canonical distribution
canonical ensemble
Gibbs state
phase transition
entropy maximization
Rényi entropy
Opis:
Entropy maximization subject to known expected values is extended to the case where the random variables involved may take on positive infinite values. As a result, an arbitrary probability distribution on a finite set may be realized as a canonical distribution. The Rényi entropy of the distribution arises as a natural by-product of this realization. Starting with the uniform distributionon a proper subset of a set, the canonical distribution of equilibriumstatistical mechanics may be used to exhibit an elementary phase transition, characterized by discontinuity of the partition function.
Źródło:
Discussiones Mathematicae Probability and Statistics; 2000, 20, 2; 167-176
1509-9423
Pojawia się w:
Discussiones Mathematicae Probability and Statistics
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 52

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