Search results for: THERMODYNAMICS
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Assessment of the impact of jet impingement technique on the energy efficiency of air-cooled BIPV/T roof tile
PublicationThe paper concerns a numerical analysis of cooling of the hybrid photovoltaic (PV) modules dedicated to Building-Integrated Photovoltaic/Thermal (BIPV/T) systems. Attention was focused on the photovoltaic roof tiles, using a jet impingement technique, in which the intensification of heat transfer is ensured by streams of air hitting the heat exchange partition. A series of numerical simulations were carried out to assess an influence...
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New empirical correlations for the viscosity of selected organic phase change materials
PublicationAlthough there are many methods and instruments for measuring viscosity, it is still difficult to determine a reliable value of the dynamic viscosity of complex chemicals such as paraffins and fatty acids. This is due to the complex and heterogeneous structure of these compounds in the case of commercial products. On the other hand, the measuring instrument should be selected very carefully, including its measuring principle and...
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Formation of bubbles from a single nucleation site.
PublicationPrzedstawiono wyniki systematycznych badań eksperymentalnych wrzenia wody destylowanej i metanolu z pojedynczego, sztucznego centrum nukleacji. Jako centra nukleacji służyły otwory wywiercone na czołowej powierzchni miedzianego pręta. Średnice otworów wynosiły: 0.25 mm, 0.60 mm oraz 1.0 mm. Do pomiaru częstotliwości odrywania się pęcherzyków zastosowano układ laser diodowy-fotodioda. Sygnał z fotodiody był rejestrowany za...
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Comparison of Downdraft and Updraft Gasification of Biomass in a Fixed Bed Reactor
PublicationThe aim of this study was to compare and analyze the gasification process of beech wood. The experimental investigation was conducted inside a gasifier, which can be operated in downdraft and updraft gasification system. The most important operating parameter studied in this paper was the influence of the amount of supply air on the temperature distribution, biomass consumption and syngas calorific value. The results show that...
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Investigations on mixture preparation for two phase adiabatic pressure drop of R134a flowing in 5 mm diameter channel
PublicationThe article presents detailed two-phase adiabatic pressure drops data for refrigerant R134a. Study cases have been set for a mass flux varying from 200 to 400 kg/m2 s, at the saturation temperature of 19.4 ◦C. Obtained experimental data was compared with the available correlations from the literature for the frictional pressure drop during adiabatic flow. Influence of mixture preparation on pressure drop was investigated, for...
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Selected studies of flow maldistribution in a minichannel plate heat exchanger
PublicationAnalysis of the state of-the-art in research of minichannel heat exchangers, especially on the topic of flow maldistribution in multiple channels, has been accomplished. Studies on minichannel plate heat exchanger with 51 parallel minichannels with four hydraulic diameters, i.e., 461 μm, 574 μm, 667 μm, and 750 μm have been presented. Flow at the instance of filling the microchannel with water at low flow rates has been visualized. The...
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The performance of H2O, R134a, SES36, ethanol, and HFE7100 two-phase closed thermosyphons for varying operating parameters and geometry
PublicationIn this study, the influences of different parameters at performance two-phase closed thermosiphon (TPCT) was presented. It has been confirmed that the working fluid, as well as operating parameters and fill ratio, are very important factors in the performance of TPCT. The article shows characteristics of gravitational tube geometr ies, as well as the technical characteristic of the most important system components, i.e., the evaporator/condenser....
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Performance of cryogenic oxygen production unit with exhaust gas bleed for sewage sludge gasification and different oxygen purities
PublicationThe paper presents a thermodynamic analysis of the integration of a cryogenic air separation unit into a negative CO2 emission gas power plant. The power cycle utilizes sewage sludge as fuel so this system fits into the innovative idea of bioenergy with carbon capture and storage. A cryogenic air separation unit integrated with the power plant was simulated in professional plant engineering and thermodynamic process analysis software....
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Optimisation of turbine shaft heating process under steam turbine run-up conditions
PublicationAn important operational task for thermal turbines during run-up and run-down is to keep the stresses in the structural elements at a right level. This applies not only to their instantaneous values, but also to the impact of them on the engine lifetime. The turbine shaft is a particularly important element. The distribution of stresses depends on geometric characteristics of the shaft and its specific locations. This means a groove manufactured...
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Thermal and economic investigation of straight and U-bend double tube heat exchanger with coiled wire turbulator
PublicationExperimental research has been carried out for four individual heat exchanger constructions, i.e., plain double tube, turbulized double tube, plain U-bend and U-bend with turbulator. Tests were made for the water-water system. The study covered a wide measuring range, i.e., Re = 800–9000 – on the shell side, for a constant cold water temperature of 9 ◦C and hot water of 50 ◦C. The heat exchangers were made from copper tubes with...
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Design and computational fluid dynamics analysis of the last stage of innovative gas-steam turbine
PublicationResearch regarding blade design and analysis of flow has been attracting interest for over a century. Meanwhile new concepts and design approaches were created and improved. Advancements in information technologies allowed to introduce computational fluid dynamics and computational flow mechanics. Currently a combination of mentioned methods is used for the design of turbine blades. These methods enabled us to improve flow efficiency...
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Computational fluid dynamics simulation of heat transfer from densely packed gold nanoparticles to isotropic media
PublicationThis work aims to determine and compare heat generation and propagation of densely packed gold nanoparticles (Au NPs) induced by a resonant laser beam (532 nm) according to the Mie theory. The heat flux propagation is transferred into the materials, which here are: silica glass; soda-lime-silica glass; borosilicate glass; polymethyl methacrylate (PMMA); polycarbonate (PC); and polydimetylosiloxane (PDMS). This analysis aims to...
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Challenges in operating and testing loop heat pipes in 500–700 K temperature ranges
PublicationThe potential applications of loop heat pipes (LHPs) are the nuclear power space systems, fuel cell thermal management systems, waste heat recovery systems, medium temperature electronic systems, medium temperature military systems, among others. Such applications usually operate in temperature ranges between 500–700 K, hence it is necessary to develop an LHP system that will meet this requirement. Such a thermal management device...
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Optimal boiling temperature for ORC installation
PublicationW pracy przedstawiono oryinalne kryterium wyznaczania optymalnej temperatury odparowania czynnika w obiegu ORC w postaci równań analitycznych. Pokazano przykład obliczeniowy na bazie R134a, wody i etanolu.
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Thermal-hydraulic issues of flow boiling and condensation in organic Rankine cycle heat exchangers
PublicationW pracy przedstawiono szereg zagadnień cieplno-przepływowych podczas wrzenia i kondensacji w przepływie w wymiennikach ciepła obiegu ORC. Uwzględniono przemiany fazowe. Analizowano zagadnienia stabilności pracy wymienników oraz ich dynamikę
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Model of heat transfer in the stagnation point of rapidly evaporating microjet
PublicationThe paper presents investigation into the single water microjet surface cooling producing evaporating film. Reported tests were conducted under steady state conditions. Experiments were conducted using the nozzle size of 70 and 100 mikrometer respectively. In the course of investigations obtained were experimental relations between heat flux and wall superheating. It was proved that the phenomenon is similar to that of pool boiling...
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Thermodynamic analysis of the double Brayton cycle with the use of oxy combustion and capture of CO2
PublicationIn this paper, thermodynamic analysis of a proposed innovative double Brayton cycle with the use of oxy combustion and capture of CO2, is presented. For that purpose, the computation flow mechanics (CFM) approach has been developed. The double Brayton cycle (DBC) consists of primary Brayton and secondary inverse Brayton cycle. Inversion means that the role of the compressor and the gas turbine is changed and firstly we have expansion...
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Power enhancement of the Brayton cycle by steam utilization
PublicationThe paper presents thermodynamic analysis of the gas-steam unit of the 65 MWe combined heat and power station. Numerical analyses of the station was performed for the nominal operation conditions determining the Brayton and combined cycle. Furthermore, steam utilization for the gas turbine propulsion in the Cheng cycle was analysed. In the considered modernization, steam generated in the heat recovery steam generator unit is directed...
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Nonlinear resultant theory of shells accounting for thermodiffusion
PublicationThe complete nonlinear resultant 2D model of shell thermodiffusion is developed. All 2D balance laws and the entropy imbalance are formulated by direct through-the-thickness integration of respective 3D laws of continuum thermodiffusion. This leads to a more rich thermodynamic structure of our 2D model with several additional 2D fields not present in the 3D parent model. Constitutive equations of elastic thermodiffusive shells...
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Solvation of ionic liquids based on N-methyl-N-alkyl morpholinium cations in dimethylsulfoxide – volumetric and compressibility studies
PublicationThe density and sound velocity of the solutions of ionic liquids based on N-alkyl-N-methyl-morpholinium cations, N-ethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide, N-butyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide, N-methyl-N-octyl-morpholinium bis(trifluoromethanesulfonyl)imide and N-decyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide in dimethylsulfoxide were measured at T = (298.15 to 318.15)...
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Effect of temperature and ionic strength on volumetric and acoustic properties of solutions of urea alkil derivatives in aqueous NaCl
PublicationThe present work was undertaken to study volumetric and acoustic properties for diluted solutions of tetramethylurea in pure water and for urea, n-propylurea, n-butylurea and tetramethylurea in 0.5 or 1 moldm3 aqueous solutions of sodium chloride. This paper presents measured values of densities and sound velocities at T = (288.15, 298.15 and 308.15) K. From these data the apparent molar volumes, , adiabatic compressibilities,...
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The hydration of the protein stabilizing agents: trimethylamine-N-oxide, glycine and its N-methylderivatives - the volumetric and compressibility studies
PublicationThe densities at T = (288.15, 293.15, 298.15, 303.15, and 308.15) K and sound velocities at T = 298.15 K have been measured for aqueous solutions of trimethylamine-N-oxide, glycine, N-methylglycine (sarcosine), N,N-dimethylglycine, N,N,N-trimethylglycine (betaine). From these data the apparent molar volumes, VΦ, the apparent molar isentropic compressions, KS,Φ, and the solvation numbers of solutes have been determined. The concentration...
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Measurement of activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-hexyl-1,4-diaza[2.2.2]bicyclooctanium bis(trifluoromethylsulfonyl)imide using gas–liquid chromatography
PublicationBased on gas–liquid chromatography (GLC) retention data, activity coefficients at infinite dilution of 39 different solutes in the ionic liquid 1-hexyl-1,4-diaza[2.2.2]bicyclooctanium bis(trifluoromethylsulfonyl)imide ([HDABCO][NTf2]) have been determined. Measurements covered a broad range of types of organic solutes including alkanes, alcohols, ketones, benzene derivatives and McReynold’s compounds. Activity coefficients were...
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Apparent molar volumes, expansibilities, and isentropic compressibilities of selected electrolytes in methanol
PublicationDensities of solutions of sodium bromide, sodium perchlorate, sodium tetraphenylborate, and tetraphenylphosphonium bromide in methanol at the temperatures ranging from 283.15 to 313.15 K have been measured. Ultrasound velocities for the above systems at T = 298.15 K have been determined. From the obtained data, the partial molar volumes and the partial molar isentropic compressibilities for electrolytes in solution have been estimated....
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Solvation of multivalent cations in methanol - apparent molar volumes, expansibilities, and isentropic compressibilities
PublicationWyznaczono gęstości roztworów trifluorometanosulfonianów galu, itru, lantanu, gadolinu i lutetu w metanolu w zakresie temperatur (283.15 to 313.15) K. Zmierzono prędkości dźwięku dla tych układów w temperaturze T = 298.15 K. Z uzyskanych danych wyznaczono standardowe cząstkowe objętości molowe i ich pochodne temperaturowe oraz standardowe cząstkowe molowe ściśliwości adiabatyczne badanych jonów. Wyniki omówiono stosując klasyczny...
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Densimetric and ultrasonic characterization of pentaerythritol in water and in aqueous NaCl and MgCl2 solutions at different temperatures
PublicationZmierzono gęstości dla serii roztworów pentaerytritolu w czystej w wodzie jak i w wodnych roztworach NaCl i MgCl2 zawierających stałą ilość soli. Pomiary wykonano dla trzech różnych zawartości NaCl i MgCl2 w sześciu rożnych temperaturch w przedziale od 20oC do 40oC. Ponadto wyznaczono szybkości rozchodzenia się dźwięku w przygotowanych roztworach dla dwóch temperatur (25 i 37oC). W oparciu o uzyskane wielkości obliczono pozorne...
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Apparent molar volumes and compressibilities of electrolytes and ions in gamma-butyrolactone
PublicationW oparciu o zmierzone wartości gęstości roztworów i rozpuszczalnika w temperaturach od 15 do 40oC wyznaczono pozorne molowe objętości bromku litu, nadchloranu litu, nadchloranu sodu, tetrafenyloboranu sodu oraz bromku tetrafenylofosfoniowego w gamma-butyrolaktonie. Ponadto, wyznaczone prędkości rozchodzenia się dźwięku w 25oC w badanych układach pozwoliły obliczyć pozorne molowe ściśliwości wybranej grupy soli. Uzyskane (w wyniku...
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Densimetric and ultrasonic characterization of urea and its derivatives in water
PublicationW oparciu o pomiary gęstości dla serii roztworów jak i rozpuszczalnika wykonanych w temperaturach 15, 20, 25, 30 i 35oC wyznaczono pozorne molowe objętości mocznika, N-metylomocznika, N,N'-dimetylomocznika, N,N,N',N'-tetrametylomocznika, N-etylomocznika, N,N'-dietylomocznika jak i N-butylomocznika w wodzie. Dodatkowe pomiary szybkości dźwięku przeprowadzone w temperaturze 25oC pozwoliły obliczyć ściśliwości adiabatyczne, pozorne...
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Apparent molar volumes and compressibilities of lanthanum, gadolinium, lutetium and sodium trifluoromethanesulfonates in N,N-dimethylformamide and N,N-dimethylacetamide
PublicationZmierzono gęstości roztworów trifluorometanosulfonianów lantanu, gadolinu i lutetu w N,N-dimetyloformamidzie i N,N-dimetyloacetamidzie w szerokim zakresie temperatur. W oparciu o uzyskane wartości gęstości wyznaczono pozorne objętości molowe, cząstkowe objętości molowe oraz rozszerzalności izobaryczne. Dodatkowo zmierzono szybkości rozchodzenia się dźwięku w badanych roztworach w 298,15 K i wyznaczono pozorne ściśliwości molowe...
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Apparent Molar Volumes and Compressibilities of Lanthanum, Gadolinium and Lutetium trifluoromethanesulfonates in Dimethylsulfoxide
PublicationZmierzono gęstości roztworów trifluorometanosulfonianów lantanu, gadolinu i lutetu w dimetylosulfotlenku w zakresie temperatur 293,15 -333,15 K. W oparciu o uzyskane wartości gęstości wyznaczono pozorne objętości molowe, cząstkowe objętości molowe oraz rozszerzalności izobaryczne. Dodatkowo zmierzono szybkości rozchodzenia się dźwięku w badanych roztworach w 298,15 K i wyznaczono pozorne ściśliwości molowe trifluorometanosulfonianów...
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Limiting Partial Molar Volumes of Tetra-n-Alkylammonium Perchlorates in N,N-dimethylacetamide, Triethylphosphate and Dimethyl Sulfoxide at 298.15 K
PublicationThe densities of tetraalkylammonium perchlorates R4NClO4(R = methyl, or ethyl, or propyl, or butyl) and ammonium perchlorate solutions in N, N - dimethylacetamide, dimethyl sulfoxide, and triethylphosphate have been measured over the whole composition range atT = 298.15 K. From these densities, apparent and limiting partial molar volumes of the electrolytes and ions...
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Volumes of N,N-dimethylacetamide solvated metal cations. Variation within the manganese(II) to zinc(II) series
PublicationDensities and apparent molar volumes for Mn(ClO4)2,Co(ClO4)2 , Ni(ClO4)2,Cu(ClO4)2 , and Zn(ClO4)2 in N, N -dimethylacetamide (DMA) solutions at T = 298.15 K are reported. Densities and apparent molar volumes of tetrabutylammonium tetraphenylborate...
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Thermophysical properties and phase equilibria study of the binary systems {N-hexylquinolinium bis(trifluoromethylsulfonyl)imide+aromatic hydrocarbons, or an alcohol}
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Studies on the solid-liquid equilibria and intermolecular interactions Urea binary mixtures with Sulfanilamide and Sulfacetamide
PublicationThe binary phase diagrams of Sulfanilamide-Urea (SN-U) and Sulfacetamide-Urea (SC-U) were measured using differential scanning calorimetry technique (DSC). Both examined mixtures were found to form simple binary eutectics. The limited miscibility in the solid state observed by DSC, proving inability of co-crystallization in new multi-molecular form, was also confirmed using PXRD and FTIR-ATR measurements of solid dispersions...
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Hydration of urea and its derivatives - Volumetric and compressibility studies
PublicationThe densities and sound velocities at T = (288.15, 293.15, 298.15, 303.15 and 308.15) K have been measured for aqueous solutions of urea, N,N-dimethylurea, N,N-diethylurea, N-propylurea, N-butylurea. From these data the apparent molar volumes, V the apparent molar isentropic compressions, KS,, and the Passynski solvation numbers of solutes have been determined. The concentration dependencies of the calculated quantities, their...
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Excess molar volume and viscosity deviation for binary mixtures of gamma-butyrolactone with dimethyl sulfoxide
PublicationThe densities of binary liquid mixtures of dimethyl sulfoxide and gamma-butyrolactone at (293.15, 298.15, 303.15 and 313.15) K and viscosity at T=298.15 K have been measured at atmospheric pressure over theentire range of concentration. From these data the excess molar volumes VE at (293.15, 298.15, 303.15 and 313.15) K and the viscosity deviation, the excess entropy, and the excess Gibbs energy of activation for viscous flow at...
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Solvation of ionic liquids based on N-alkyl-N-methylmorpholinium cations in N,N-dimethylformamide and dimethyl sulfoxide – A volumetric and acoustic study
PublicationApparent molar volumes and molar isentropic compressibilities for N-ethyl-N-methylmorpholinium and N-decyl-N-methylmorpholinium tetrafluoroborates in N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) have been determined from density and speed of sound measurements over the temperature range T = (298.15, 303.15, 308.15, 313.15, 318.15 and 328.15) K at experimental pressure p = 0.1 MPa. This data has been used to calculate...
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On existence and uniqueness of weak solutions for linear pantographic beam lattices models
PublicationIn this paper, we discuss well-posedness of the boundary-value problems arising in some “gradientincomplete” strain-gradient elasticity models, which appear in the study of homogenized models for a large class ofmetamaterials whosemicrostructures can be regarded as beam lattices constrained with internal pivots. We use the attribute “gradient-incomplete” strain-gradient elasticity for a model in which the considered strain energy...
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Sensitivity analysis of free torsional vibration frequencies of thin-walled laminated beams under axial load
PublicationThe paper addresses sensitivity analysis of free torsional vibration frequencies of thin-walled beams of bisymmetric open cross-section made of unidirectional fibre-reinforced laminate. The warping effect and the axial end load are taken into account. The consideration is based upon the classical theory of thin-walled beams of non-deformable cross-section. The first-order sensitivity variation of the frequencies is derived with...
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Adaptation of the arbitrary Lagrange–Euler approach to fluid–solid interaction on an example of high velocity flow over thin platelet
PublicationThe aim of this study is to analyse the behaviour of a thin plate with air flow velocities of 0.3–0.9 Ma. Data from the experiment and numerical tools were used for the analysis. For fluid–solid interaction calculations, the arbitrary Lagrange–Euler approach was used. The results of the measurements are twofold. The first one is the measurement of the flow before and after vibrating plate, i.e. pure flow plate, and the second consists...
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Apparent molar volumes and compressibilities of selected electrolytes in dimethylsulfoxide
PublicationDensities at T = (293.15, 298.15, 303.15, 313.15, 323.15, and 333.15) K and sound velocities at T = 298.15 K of tetraphenylphosphonium bromide, sodium tetraphenylborate, sodium bromide, and sodium perchlorate in dimethylsulfoxide have been measured over the composition range from (0 to 0.3) mol kg1. From these data, apparent molar volumes and apparent molar isentropic compressibilitiesat infinite dilution as well as the expansibilities...
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Apparent molar volumes and compressibilities of alkaline earth metal ions in methanol and dimethylsulfoxide
PublicationTemperature dependencies of density of magnesium (II), calcium (II), strontium (II), barium (II) perchlorates as well as beryllium (II), and sodium trifluoromethanesulfonates in methanol and dimethylsulfoxide have been determined over the composition range studied. From density data the apparent molar volumes and partial molar volumes of the salts at infinite dilution as well as the expansibilities have been evaluated. The apparent...
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Apparent molar volumes and compressibilities of tetrabutyl-ammonium bromide in organic solvents
PublicationW oparciu o pomiary gęstości i szybkości rozchodzenia się dźwięku w niewodnych roztworach bromku czterobutyloamoniowego obliczono pozorne objętości molowe w przedziale temperatur od 288,15 K do 323,15 K oraz pozorne ściśliwości w temperaturze 298,15 K. Graniczne wielkości pozornej objętości molowej i ściśliwości wyznaczono w oparciu o równanie Massona, jak i równanie Redlicha, Rosenfelda i Mayera oraz z wykorzystaniem teorii Pitzera....
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Solvation of ionic liquids based on N -methyl- N -alkylmorpholinium cations in N,N -dimethylformamide and N,N -dimethylacetamide – Volumetric and compressibility studies
PublicationDensity and sound velocity of the solutions of ionic liquids based on N-alkyl-N-methyl- morpholinium cations: N-ethyl- -methylmorpholinium bis(trifluoromethanesulfonyl)imide, N-butyl-Nmethylmorpholinium bis(trifluoromethanesulfonyl)imide, N-octyl-N-methyl -morpholinium bis(trifluor omethanesulfonyl)imide and N-decyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide in N, N-dimethylformamide and N,N-dimethylacetamide were...
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Virtual spring damper method for nonholonomic robotic swarm self-organization and leader following
PublicationIn this paper, we demonstrate a method for self-organization and leader following of nonholonomic robotic swarm based on spring damper mesh. By self-organization of swarm robots we mean the emergence of order in a swarm as the result of interactions among the single robots. In other words the self-organization of swarm robots mimics some natural behavior of social animals like ants among others. The dynamics of two-wheel robot...
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Local buckling of composite channel columns
PublicationThe investigation concerns local buckling of compressed flanges of axially compressed composite channel columns. Cooperation of the member flange and web is taken into account here. The buckling mode of the member flange is defined by rotation angle a flange about the line of its connection with the web. The channel column under investigation is made of unidirectional fibre-reinforced laminate. Two approaches to member orthotropic...
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Structural response of existing spatial truss roof construction based on Cosserat rod theory
PublicationPaper presents the application of the Cosserat rod theory and newly developed associated finite elements code as the tools that support in the expert-designing engineering practice. Mechanical principles of the 3D spatially curved rods, dynamics (statics) laws, principle of virtual work are discussed. Corresponding FEM approach with interpolation and accumulation techniques of state variables are shown that enable the formulation...
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Nonlinear finite element modeling of vibration control of plane rod-type structural members with integrated piezoelectric patches
PublicationThis paper addresses modeling and finite element analysis of the transient large-amplitude vibration response of thin rod-type structures (e.g., plane curved beams, arches, ring shells) and its control by integrated piezoelectric layers. A geometrically nonlinear finite beam element for the analysis of piezolaminated structures is developed that is based on the Bernoulli hypothesis and the assumptions of small strains and finite...
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Pantographic metamaterials: an example of mathematically driven design and of its technological challenges
PublicationIn this paper, we account for the research efforts that have been started, for some among us, already since 2003, and aimed to the design of a class of exotic architectured, optimized (meta) materials. At the first stage of these efforts, as it often happens, the research was based on the results of mathematical investigations. The problem to be solved was stated as follows: determine the material (micro)structure governed by those...
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Selected local stability problems of channel section flanges made of aluminium alloys
PublicationThe paper addresses the issue of local buckling of compressed flanges of cold-formed thin-walled channel columns and beams with nonstandard flanges composed of aluminium alloys. The material behaviour follows the Ramberg–Osgood law. It should be noted that the proposed solution may be also applied for other materials, for example: stainless steel, carbon steel. The paper is motivated by an increasing interest in nonstandard cold-formed...